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Recent problems solved by 'rapaljer'
rapaljer answered: 4664 problems
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Answer 7543 by rapaljer(4667) on 2005-10-13 16:15:19 (Show Source):
You can put this solution on YOUR website!The rule that I use is not the way most people teaching math use, but I like it. Whenever you have an equation with a
POSITIVE coefficient of y > or >= , you must shade ABOVE the line.
POSITIVE coefficient of y < or <= , you must shade BELOW the line.
That's as simple as it gets! Examples:
2x+3y < 6 Shade Below
2x+3y > 6 Shade Above
2x+3y >= 6 Shade Above
2x+3y <= 6 Shade Below
So, what if you have a NEGATIVE COEFFICIENT of Y? Well, if you multiply both sides of an inequality by a negative, this reverses the inequality, and therefore it REVERSES the RULE!!
2x - 3y < 6 same as -2x+3y> -6 Shade Above!!
See if that helps. If you need more, I might be able to send you a section from my book in a word file.
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Numbers_Word_Problems/15189: What would be another way to add 1+3+5+7+9+....499=to equal the sum of 62,500?
Only using odd numbers. We need another way to find the sum of all the odd numbers from 1 to 499 and equal 62,500
1 solutions
Answer 7540 by rapaljer(4667) on 2005-10-13 16:05:45 (Show Source):
You can put this solution on YOUR website!1+3+5+7+9+....499
Before you begin, notice that you are adding numbers from 1 to 499, omitting the even numbers in between, so there will be a total of 250 numbers that are added together.
Pair these numbers up by adding 1+499, 3+497, 5+495, etc.
Notice that each sum is 500, and the number of such pairs will be half of the 250 numbers that are added together, or 125. Therefore, the sum will be 500 times 125 = 62500.
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Quadratic_Equations/15188: When solving a rational equation, why it is OK to remove the denominator by multiplying both sides by the LCD and why can you not do the same operation when simplifying a rational expression or adding rational expressions?
The only answere that I have come up with so far is the one is an expression and one is an equation. With the equation we are solving for a variable, and with an expression we are simplyfying and then doing what is required ie, add, subtract, multiple or divide. Is there more to this question that I am missing?
1 solutions
Answer 7539 by rapaljer(4667) on 2005-10-13 15:58:26 (Show Source):
You can put this solution on YOUR website!This is one of my favorite questions, and I answer it every day! If you have an EQUATION, then the multiplication property of equations allows you to multiply BOTH SIDES of an EQUATION by the same NON-ZERO number. However, if you have a rational EXPRESSION, then you do NOT have an equation, so the properties of EQUATIONS do NOT apply! Moreover, you can't solve an expression. About all you can do with expressions is add, subtract, multiply, divide, simplify or factor them.
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Quadratic_Equations/15166: Help! I've been trying to solve this problem and am stuck.
Three consecutive numbers are multiplied together to get 24. Can you help? 1 solutions
Answer 7537 by rapaljer(4667) on 2005-10-13 14:31:01 (Show Source):
You can put this solution on YOUR website!The equation for this one will be somewhat complicated to solve, but the answer is easy to find. Think about this: Three consecutive numbers whose product is 24. It's a pretty small number, so start small and use trial and error. Start with 2 for the first number. This makes the second number 3, and the third number is 4. Does that work? 2*3*4 = 24. Bingo!!
The equation is to let x = first, x+1= second, and x+2= third.
The equation is x(x+1)(x+2)= 24. This gets ugly fast. If you multiply it out you will get  , which is a tough equation to solve without higher math. If that is what you need, then resubmit the question, and someone will solve it for you.
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Reduction-of-unit-multipliers/15163: the speed of a trian is 24 km per hour. What is it approximate speed in cm per second?
and i need the work 1 solutions
Answer 7535 by rapaljer(4667) on 2005-10-13 14:15:19 (Show Source):
You can put this solution on YOUR website!First to change km to m, multiply by 1000, and to change from m to cm, you must multiply by 100. In other words multiply by 100,000. To change from a time per hour to a time per second, you must divide by 3600 (that is, 60 minutes in an hour and 60 seconds in a minute).
Final answer then is to do take  = 666.67 cm/sec.
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Miscellaneous_Word_Problems/15167: to stimulate his daughter in the pursuit of problem solving, a math professor offered to pay her $8 for every equation correctly solved and to fine her $5 for every incorrect solution. At the end of the first 26 problems of this problem set, neither owed any money to the other. How many problems did the daughter solve?
I found out the answer is ten I don't know how to set this problem up to get the answer 10. 1 solutions
Answer 7534 by rapaljer(4667) on 2005-10-13 14:08:14 (Show Source):
You can put this solution on YOUR website!If there are 26 problems, let x = number right, and therefore the number wrong will be all the rest, which is 26-x. The equation is due to the fact that 8 times the number right minus 5 times the number wrong equals zero.
8x - 5(26-x) = 0
8x - 130 + 5x = 0
13x - 130=0
13x -130 + 130 = 0+130
13x = 130
x= 10 Questions right
26-10 = 16 Questions wrong
Check: $8*10 - $5*16 = 0
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Probability-and-statistics/15121: If a couple plans to have eight children, find the probability that they are all of the same gender.
Thanks a lot. 1 solutions
Answer 7520 by rapaljer(4667) on 2005-10-13 00:30:17 (Show Source):
You can put this solution on YOUR website!The probability of having a boy is 1/2, and the probability of having a girl is also 1/2.
To find the probability of having successive children of a particular gender, assuming that the birth of each child is independent of every other child is the product of the probabilities. Suppose the first child born determines the gender, boy or girl, of all the other children. Therefore, if there are 8 children, the probability that the succeeding SEVEN children will match the gender of the first child will be
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expressions/15058: CAN SOMEONE FIND The answer to 6y-(3y+9)=17 1 solutions
Answer 7494 by rapaljer(4667) on 2005-10-12 18:36:27 (Show Source):
You can put this solution on YOUR website!First remove the parentheses. Don't forget the negative sign on the 9:
6y-(3y+9)=17
6y - 3y - 9 = 17
3y - 9 = 17
Next add + 9 to each side:
3y- 9 + 9 = 17 + 9
3y = 26
Divide both sides by 26.
It doesn't come out even, but then life doesn't always come out even, does it!
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Graphs/15044: Hi.
I have a question about solving linear equations. How would you solve X+Y=4? If you can help me solve just that one, then Ill know how to do the rest.
Thanks Alot
Sara 1 solutions
Answer 7491 by rapaljer(4667) on 2005-10-12 18:28:31 (Show Source):
You can put this solution on YOUR website!The equation x+y=4 is in what is called "standard form" where you have an x term plus (or minus) a y term = a number term. When this happens, I think the easiest way to graph it (usually) is to graph the two easiest points that you can, the x and y intercepts. The first points is found by letting x= 0 and find y (that would be the y-intercept!). Second point is found by letting y=0 and find x (that would be the x-intercept!).
In this case, if x = 0, y = 4.
If y=0, then x = 4.
Plot these two points: (0,4) and (4,0). Connect the points with a line, and continue the line in both directions. It should look like this:
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Graphs/15047: Hello
I am trying to go back to school I have never liked math. Now that I need to take a test to enter college I am confused I have the THEA guide book. But they really don't explain to well the problems. Anyways I am trying to figure this out 2x+3y=6 I need to graph but first I need to solve for x and then solve for Y. Please I hope you can help me!!!! 1 solutions
Answer 7490 by rapaljer(4667) on 2005-10-12 18:22:16 (Show Source):
You can put this solution on YOUR website!I'm not familiar with the THEA guide book, but when you are graphing an equation like 2x + 3y = 6, I can't imagine why you would want to solve for x. Solving for y is a nice idea, but I don't think that is the easiest way to graph this equation.
Nevertheless, solve for y by adding -2x from both sides:
2x + 3y = 6
2x-2x + 3y = -2x + 6
3y = -2x + 6
Next, divide both sides by 3 in order to solve for y.
3y= -2x + 6
What this means is the the y intercept is 2, and the slope (steepness!) of the line is -2/3.
Start with an xy graph, and go up two units on the y-axis and put a point. Next, with your pencil on this point on the y axis, measure off the slope which is a rise of -2 followed by a run of 3. This means from the point you made at y=2 on the y-axis, count DOWN 2 units, and go RIGHT 3 units, and put another point. Then connect the points with a line, and extend the line in both directions. The result should look like this:
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Graphs/15053: y=2 1 solutions
Answer 7489 by rapaljer(4667) on 2005-10-12 18:10:23 (Show Source):
You can put this solution on YOUR website!Oh, I get it! Now we are playing Jeopardy! The answer is 2. What was the question??
"What is the solution to the equation 4y + 16 = 24?"
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Seriously, you probably wanted to graph the equation y=2. Anytime you graph y= a number (with no x in the equation). It is a horizontal line. So on an xy graph, go up two units on the y-axis, and draw a horizontal line. That's it!
If you ever have an equation like x = 2 (with no y in the equation), then you have a vertical line.
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Radicals/14985: Unable to come up with the correct solution. (2y/x^2)+(7/x(x-3)). The solution I came up with was 2y+7/x^2(x-3) 1 solutions
Answer 7445 by rapaljer(4667) on 2005-10-12 01:06:31 (Show Source):
You can put this solution on YOUR website!First the LCD for this problem is  . You must multiply the first fraction numerator and denominator by (x-3), and you must multiply the second denominator by x. Did you follow all of that?
 .
 .
 .
I think that's about all you can do with it. You can rearrange the numerator, but it doesn't simplify anything, and it doesn't factor.
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Linear_Algebra/14983: You have two boxes of the same shape that hold flour. The larger box holds twice as much flour as the smaller one. You conclude that it would take you ?? times as much paint to paint the lager box then it would take you to paint the smaller box. 1 solutions
Answer 7443 by rapaljer(4667) on 2005-10-12 00:54:32 (Show Source):
You can put this solution on YOUR website!Let V = volume of the smaller box. Since  , where x is the length of the side of each square side, each side of this box will be  , and the area of each face of the box will be  .
Now, the larger box has twice the volume or 2V, where  , where y is the length of the side of each square side. Each side of this box will be  , and the area of each face of the box will be  .
Notice that the larger box has area of each face that is similar to the face of the smaller of the box, except that it is multliplied by  power. This computes to a surface area that is about 1.587 times as much as the smaller box, so it should take about 1.587 times as long to paint the box. Hey, it's late in Florida right now, and maybe someone will check this out and make sure I'm right!! Any volunteers??
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Functions/14979: I need to develop a function that represents the following conditions:
A car was purchased for $22,500. The value of the car decreases by $3200 per year for the first six years. Write a function that describes the value of the car, V, after x years, where x is greater than or equal to 0 but less than or equal to 7. Then find and interpret V(3).
V(x)=22,500-3200(x)
v(3)=22,500-3200(3)
That would be my best guess. Thanks for your help! 1 solutions
Answer 7440 by rapaljer(4667) on 2005-10-12 00:21:48 (Show Source):
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Linear_Algebra/14981: YOu have a 5 foo ladder , and you lean it against a wall such that the bottom of th eladder is 3 fee away from the wall. the top of the ladder touches the wall at a height of ?? feet. 1 solutions
Answer 7438 by rapaljer(4667) on 2005-10-12 00:14:39 (Show Source):
You can put this solution on YOUR website!In my very last solution that I posted not 5 minutes ago, this same concept came up. This is a right triangle whose hypotenuse is the 5 foot ladder. It reaches the wall 3 feet from the wall, which is the first leg, and the second leg is the unknown x, which is the distance up the wall where the ladder reaches at the top.
If you are familiar with the special right triangle whose sides are 3, 4, 5, or any multiple thereof, then you recognize that the unknown side is 4 feet.
If you are NOT familiar with these special triangles, then you solve the equation

x=4 feet.
Either way, the unknown side of the right triangle is 4 feet (up the wall!).
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Linear_Algebra/14982: A 10 foot plank is used to brace a basement wall during construction of a home. the plank is nailed to the wall 6 feet above the floor the slope of the plank is ??. 1 solutions
Answer 7437 by rapaljer(4667) on 2005-10-12 00:07:11 (Show Source):
You can put this solution on YOUR website!The board forms a right triangle, where the board itself is the hypotenuse, and the legs will be the sides of the right triangle which are 6 and x, the unknown side on the floor between where the board reaches the floor and the wall.
If you are familiar with the special right triangle whose sides are 3, 4, 5, or any multiple thereof, then you are familiar with a right triangle whose sides are double these numbers: 6, 8, 10, so the unknown side is 8 feet.
If you are NOT familiar with these special triangles, then you solve the equation

x=8 feet.
Either way, the unknown side of the right triangle is 8 feet.
Now, the slope is the rise over the run, where rise is 6 feet, and the run is 8 feet. Therefore the slope is
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Numeric_Fractions/14977: complete the next two terms for the following sequence:-
5/7, 3/4, 7/9, 5/4, , , 1 solutions
Answer 7436 by rapaljer(4667) on 2005-10-11 23:58:09 (Show Source):
You can put this solution on YOUR website!The first step is to figure out the pattern. First look to see if there is a common number that you multiply the first number times to get the second, then the third, the fourth, etc. It doesn't look like there is a common factor that will do this, so it is not what we call a geometric sequence.
Second, see if there is a common number that can be added to get from the first number to the second, second to third, etc. Since there is no obvious common denominator, this does not appear to be the case.
So, see if there is a number that you can add to numerator and denominator that would make sense. Also, be aware that in the process of doing this, some of the fractions may have already been reduced to lowest terms. Try adding 1 to the numerator and denominator of 5/7. That would give you 6/8 which reduces to 3/4.
Continue by taking 6/8 and add 1 to the numerator and denominator. This gives 7/9 which is the third number.
Next, add 1 to numerator and denominator of 7/9 which would be 8/10 or 4/5. This is too close to what you have given as 5/4. I think maybe did you copy the problem wrong? If so, the PROBLEM should be
5/7, 3/4, 7/9, 4/5, , ,
The PATTERN would be the
5/7, 6/8, 7/9, 8/10, 9/11, and 9/12 or 3/4
And the SOLUTION would be the last two numbers in the sequence:
9/11 and 3/4.
If indeed you DID copy the problem correctly, then I am wrong. Please disregard this solution, and re-post the question, with my sincere apologies!!
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Linear-equations/14975: I must find a linear equation in slope-intercept form that models the following description. I must also indicate what each variable represents.
In 1995, the average temperature on Earth was 57.7 degrees F and has increased at a rate of 0.01 degrees F per year since then.
My guess of the equation would be: y=.01x + 57.7
y=the temperature
x=number of years 1 solutions
Answer 7435 by rapaljer(4667) on 2005-10-11 23:42:23 (Show Source):
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Triangles/11744: If I have a triangle with one side equalling 8 feet, another side equalling 12 feet, and I have to find the third side (which is the longest), what do I do? 1 solutions
Answer 7404 by rapaljer(4667) on 2005-10-11 19:51:41 (Show Source):
You can put this solution on YOUR website!Is this a right triangle? Assuming that it is a RIGHT triangle, where c is the hypotenuse, and a and b are legs,
 , where in this case, the hypotenuse is the longest, which is the unknown, and a and b are 8 and 12 respectively.
 or
c is the side of a triangle and therefore cannot be negative.
 =  feet
You might want to calculate this and round to nearest hundredth:
 feet
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Systems-of-equations/13945: 3n+10/n+17
How do I do it? 1 solutions
Answer 7003 by rapaljer(4667) on 2005-10-05 00:35:02 (Show Source):
You can put this solution on YOUR website!First of all, I'm not sure what you want to do with this. Secondly, I'm not sure exactly what you meant for the fraction. Do you mean just the fraction of 10 divided by n? Do you mean the fraction of 3n+10 divided by the quantity of n+17? It's not clear what you want. So, I'll take a shot at what I think you mean, which is exactly what it says:
Find a common denominator which is n, and multiply the first and last terms by  .
Factor, just because it does factor!
Does that do it?
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Linear-systems/13955: I need some help on solving this problem: The vertical blue stripe in the bristles of the toothbrush wears down linearly to half its original length in 90 days of regular use. After the toothebrush has been used regularly for 2 weeks and 4 days, what fractional part of this blue stripe still remains??
The choices are A) 1/10 B) 1/5 C)2/5 D)3/4 E)9/10
I need some help with this...thank you...its greatly appreciated! 1 solutions
Answer 6999 by rapaljer(4667) on 2005-10-05 00:06:14 (Show Source):
You can put this solution on YOUR website!If the toothbrush wears down to half of its length in 90 days linearly, then it will wear out the rest of the way in another 90 days, for a total of 180 days to wear completely out.
Since 2 weeks and 4 days is a total of 18 days, that would be 1/10 of the total life of the toothbrush. This means that 10% has been used up, and 90% remains. I would say the answer is E) 9/10.
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Equations/13617: I am trying to determine what the rule is when there is a - outside of the brakcets.
In one problem, I am multiplying by the LCD 15... and it's .
In another problem, I am multiplying by the LCD 20... and it's .
What is the rule? Why is it -15 but +10?? I am perplexed again, but if I can figure this out in words I think I'll be OK. Can you help? 1 solutions
Answer 6873 by rapaljer(4667) on 2005-10-03 06:58:55 (Show Source):
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Miscellaneous_Word_Problems/13618: i get one banana for two apples if one apple cost rs two rupees than how many banans will i get for rs 13 rupees? 1 solutions
Answer 6872 by rapaljer(4667) on 2005-10-03 06:53:28 (Show Source):
You can put this solution on YOUR website!If 1 banana = 2 apples
1 apple = 2 rupees
Then 1 banana = 4 rupees
3 bananas = 12 rupees.
So for 13 rupees you can get 3 bananas and have 1 rupee left over. Can you buy  of a banana? If so, then you can buy 3  bananas!
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Finance/13388: hi,
im a nursing student and were going to have problems regarding solutions.my prof. want us to relate nursing to algebra.can you give us exaples in it?????
i hope you can help me.
big tnx. 1 solutions
Answer 6799 by rapaljer(4667) on 2005-10-01 21:11:34 (Show Source):
You can put this solution on YOUR website!I have a page on my website that may be what you are looking for. This is the URL if it comes through as such:
http://www2.seminolestate.edu/rrapalje/Tech-Prep-Math/Metric%20System.htm
In case that doesn't show up as a URL that you can click on, go to my website by clicking on my user name anywhere in algebra.com, then look for a topic called "Tech Prep" in the second column near the bottom of the page. Click on that, and look for "Metric System", which is a rather long handout. Scroll down near the end of that "Metric System" page, and you will find a section devoted to "Medical Applications--Dosages". It might help.
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