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# Recent problems solved by 'edjones'

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 percentage/180976: Two hundred and seventy students wrote an exam in which 35 students got a higher mark than Paula and eight got the same mark as Pauls, which is 83%. Her percentile rank in the class is? a. 85 b. 86 c. 83 d. 841 solutions Answer 135689 by edjones(7569)   on 2009-02-09 00:08:58 (Show Source): You can put this solution on YOUR website!235, 234, 233, 232, 231, 230, 229, 228, are all tied. Their mean is 231.5 n=Np/100+.5 Where n=numerical rank, N=number of values, p=percentile 231.5=270p/100 + .5 2.7p=231 p=85.556 p=86 . Ed
 Miscellaneous_Word_Problems/181003: I have a problem where I figured it out like this. I need 30 tons of rocks to cover an area. If each ton costs \$60 and each tree is \$84, what is the maximum amount of trees I can buy with a budget for rock and trees of \$2,500? I answered: (30)(60) + 84T<2500 1800 + 84T <2500 84T<700 T<8.33333... The second part asks if 5 trees could be a solution, I said no because the answer is 8 but I don't know how to show proof?1 solutions Answer 135687 by edjones(7569)   on 2009-02-08 23:27:42 (Show Source): You can put this solution on YOUR website!The 1st part of your answer is all the proof you need.
 Travel_Word_Problems/181012: Juan rides his bike from Lawrence to Salisbury beach (30 miles in 3 hours). He divides distance (miles) by time (hours) and sees that his overall average speed is 10mph. He buys 3 Power bars and eats them. How fast (mph) must he return so that his overall average speed for the round trip (60 miles) is 15mph?1 solutions Answer 135686 by edjones(7569)   on 2009-02-08 23:18:11 (Show Source): You can put this solution on YOUR website!Let x be the speed he must go on the return trip. (10+x)/2=15 10+x=30 x=20 mph . Ed
 Average/180921: Scientific notation: Simplify b^3p^4/(bp)^21 solutions Answer 135653 by edjones(7569)   on 2009-02-08 18:00:29 (Show Source): You can put this solution on YOUR website!b^3p^4/(bp)^2 *** (bp)^2=b^2p^2 =bp^2 subtract exponents when dividing. . Ed
 Polynomials-and-rational-expressions/180746: The simplified form of x+5/5-x - 3/x^2-25 is ?1 solutions Answer 135652 by edjones(7569)   on 2009-02-08 17:51:15 (Show Source): You can put this solution on YOUR website!x+5/5-x - 3/x^2-25 =[x+5/5-x] - [3/(x+5)(x-5)]Factor denominator. =[(x+5)^2-3]/[(x+5)(x-5)] =(x^2+10x+22)/(x^2-25) . Ed
 Miscellaneous_Word_Problems/180887: This question is from textbook 1000 tickets for prizes are sold for \$2 each. Seven prizes will be awarded – one for \$400, one for \$200, and five for \$50. Steven purchases one of the tickets. a) Find the expected value b) Find the fair price of the ticket. 1 solutions Answer 135650 by edjones(7569)   on 2009-02-08 17:38:05 (Show Source): You can put this solution on YOUR website!you have 7 chances to win a total of 850 -2 * (1000-7)/1000=-993/500 850/7 * 7/1000=17/20 17/20 - 993/500=-142/125 or -\$1.136 EV Since the EV is negative you will lose \$1.136 for every \$2 ticket you buy. . Fair price of a ticket = 850/1000=\$.85 . Ed
Complex_Numbers/180850: a boy buys x eggs at (x-8) cents each and (x-2) rashers of bacon at (x-3) cents each. if the total bill is \$1.75, how many eggs does he buy?
1 solutions

Answer 135641 by edjones(7569)   on 2009-02-08 16:41:53 (Show Source):
You can put this solution on YOUR website!
x(x-8)+(x-2)(x-3)=175
x^2-8x+x^2-5x+6=175
2x^2-13x-169=0
x=13
.
Ed
.
 Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc) Quadratic equation (in our case ) has the following solutons: For these solutions to exist, the discriminant should not be a negative number. First, we need to compute the discriminant : . Discriminant d=1521 is greater than zero. That means that there are two solutions: . Quadratic expression can be factored: Again, the answer is: 13, -6.5. Here's your graph:

 Probability-and-statistics/180914: In a shipment of 100 televisions, 6 are defective. If a person buys two televisions from that shipment, what is the probability that both are defective?1 solutions Answer 135639 by edjones(7569)   on 2009-02-08 16:09:28 (Show Source): You can put this solution on YOUR website!6/100 chance 1st one is defective. 5/99 chance 2nd is defective 6/100 * 5/99 = 30/990 =1/33 . Another way: nCr=2C6=15 nCr=2C100=4950 15/4950=1/33 . Ed
 Probability-and-statistics/180889: This question is from textbook A license plate is to consist of two letters followed by three digits. How many different license plates are possible if the first letter must be a vowel, and repetition of letters is not permitted, but repetition of digits is permitted? 1 solutions Answer 135637 by edjones(7569)   on 2009-02-08 15:51:31 (Show Source): You can put this solution on YOUR website!VLDDD any one of 5 vowels may be the 1st letter. any one of 25 letters may be the second letter. any of 10 digits 3 times are the last 3. 5*25*10^3=125,000 different plates are permitted. . Ed
 Miscellaneous_Word_Problems/180474: if you have 1-42 range.what are the possible 6 digit number combination that you can have?note:numbers should not be repeated in every combination.tell all the possible combination. 1 solutions Answer 135345 by edjones(7569)   on 2009-02-06 01:07:04 (Show Source): You can put this solution on YOUR website!9C6=84 Combinations of numbers 1-9 only 9C4*(42-9)=126*33=4158 Combinations of 1-9 and one of the other 33 numbers. 9C2*33C2=36*528=19008 Combinations of 1-9 and two of the other 33 numbers. 33C3=5456 Combinations of 3 of the other 33 numbers. 84+4158+19008+5456=28,706 . Ed
 Radicals/180529: 5^(4/3) * 5^x = 251 solutions Answer 135344 by edjones(7569)   on 2009-02-06 00:59:52 (Show Source): You can put this solution on YOUR website!5^(4/3) * 5^x = 25 log[5]5^(4/3)*log[5]5^x=log[5]5^2 4x/3=2 4x=6 x=2/3 . Ed
 Miscellaneous_Word_Problems/180547: This question is from textbook Find the perimeter and area of a right triangle if the shortest side is 9cm and the longest side is 15cm. Can you explain please...1 solutions Answer 135342 by edjones(7569)   on 2009-02-06 00:41:39 (Show Source): You can put this solution on YOUR website!a^2+b^2=c^2 Let b=9 and c=15 The hypotenuse is the longest line in a right triangle. a^2+9^2=15^2 a^2+81=225 a^2=144 a=12 12+9+15=36 cm . Ed
 Equations/180590: Hi. I'm checking to see if I got this problem correct. Solve the equation. 3y/4-13=-y/3 thanks H.C.1 solutions Answer 135341 by edjones(7569)   on 2009-02-06 00:31:33 (Show Source): You can put this solution on YOUR website!3y/4 - 13=-y/3 9y-156=-4y 13y=156 y=12 . Ed
 Linear-equations/180215: y=-1.5x-4 x=-21 solutions Answer 135166 by edjones(7569)   on 2009-02-05 03:41:45 (Show Source): You can put this solution on YOUR website!y=-1.5x-4 x=-2 . y=(-1.5*-2)-4 y=3-4 y=-1 . Ed
 Equations/180268: x2-4x-41 solutions Answer 135165 by edjones(7569)   on 2009-02-05 03:29:06 (Show Source): You can put this solution on YOUR website!x^2-4x-4 The sum of the two factors of -4 equal -4 and the signs are different. =(x-4)(x+1) . Ed
 Permutations/180289: For the same price you can order a basic pizza and add any two extra toppings from a choice of six different toppings. If a double of one topping is allowed, the number of different pizzas with two toppings is?1 solutions Answer 135164 by edjones(7569)   on 2009-02-05 03:22:07 (Show Source): You can put this solution on YOUR website!6C2+6 =15+6 =21 different pizzas. . Ed
 Radicals/180295: the solution square root x+1 + square root x + 2=1 is contained in the interval?1 solutions Answer 135163 by edjones(7569)   on 2009-02-05 03:14:57 (Show Source): You can put this solution on YOUR website!sqrt(x+1)+sqrt(x+2)=1 2x+2sqrt(x+1)sqrt(x+2)+3=1 square each side 2sqrt(x+1)sqrt(x+2)=-2x-2 4(x+1)(x+2)=4x^2+8x+4 square each side 4x^2+12x+8=4x^2+8x+4 4x+4=0 subtract the right side from the left. 4x=-4 x=-1 . Ed
 Expressions-with-variables/179692: 118. Solve if it has a solution SR(x – 2) + 5 = 1 129. Simplify 64^(2/3) 1 solutions Answer 134613 by edjones(7569)   on 2009-02-02 02:32:40 (Show Source): You can put this solution on YOUR website!sqrt(x–2)+5=1 sqrt(x-2)=-4 x-2=16 square each side x=18 . Check: sqrt(18-2)+5=1 4+5=1 False. . There is no answer. . Simplify 64^(2/3) 64^(1/3)=4 4^2=16 . Ed
 Quadratic_Equations/179156: Please help. Find b^2 _4ac and the number of real solutions to each equation. 1. 9m^2 + 16 = 24m 2. -3x^2 + 7x =01 solutions Answer 134481 by edjones(7569)   on 2009-02-01 00:27:47 (Show Source): You can put this solution on YOUR website!ax^2+bx+c=0 . 9m^2 + 16 = 24m 9m^2-24m+16=0 Now it is in the correct form. b^2-4ac =24^2-(4*9*16) =576-576 =0 There is one real answer because b^2-4ac is zero. . -3x^2+7x=0 There is no constant, c so c=0. b^2-4ac =7^2-(4*-3*0) =49-0 =49 There are 2 real solutions because b^2-4ac is positive. . Ed
 Quadratic_Equations/179535: Solve by factoring: x^2-5x=6 Thanks for your help and time ;)1 solutions Answer 134478 by edjones(7569)   on 2009-02-01 00:05:14 (Show Source): You can put this solution on YOUR website!x^2-5x=6 x^2-5x-6=0 What factors of -6, with different signs, add up to -5? Ans: -6, +1 (x-6)(x+1)=0 x=6, x=-1 . Ed
 Quadratic_Equations/179282: Matt makes a cardboard frame to go around the edges of an 8cm * 10cm photograph. The frame has an area of 63 square centimeters and is of equal width all the way around. What is the width?1 solutions Answer 134383 by edjones(7569)   on 2009-01-31 01:22:02 (Show Source): You can put this solution on YOUR website!L*w=A 10*8=80 Let x be the increase in length or width in the frame compared to the picture. (x+10)(x+8)=63+80 x^2+18x+80=143 x^2+18x-63=0 (x+21)(x-3)=0 x=3 . Ed
 Graphs/179289: 1/4(8y+4)-34<-1/3(9y-6) Solve inequality and graph1 solutions Answer 134381 by edjones(7569)   on 2009-01-31 01:02:40 (Show Source): You can put this solution on YOUR website!1/4(8y+4)-34<-1/3(9y-6) 2y+1-34<-3y+2 2y-33<-3y+2 5y<35 y<7 . Ed
 Functions/179180: This question is from textbook College Mathematics I am looking for the domain and the range for the equation: x^2+y = 10 I thought that the square root of a negative number was imaginary and, as such we could not have a function from this equation. Apparently, this is not correct. Can you please explain what are and how to find the domain and range here?1 solutions Answer 134133 by edjones(7569)   on 2009-01-29 12:32:48 (Show Source): You can put this solution on YOUR website!y=ax^2+bx+c the form of a quadratic equation. y=-x^2+10 a=-1, b=0 c=10 a is negative so the parabla has a maximum (opens downward). The domain (of x) is all real numbers. . The maximum is (-b^2-4ac)/4a (-0^2-(4*-1*10))/4 =40/4=10 . The range (for y) is 10 to, but not including, -infinity or [10, -infinity) . Ed .
 Linear_Equations_And_Systems_Word_Problems/179159: Write a system of two equations in two unknowns for each problem. Solve each system by the method of your choice. Please help!!! I'm having the hardest time with this. Thanks The probability that San Francisco plays in the next Super Bowl is nine times the probability that they do not play in the next Super Bowl. The probability that San Francisco plays in the next Super Bowl plus the probability that they do not play is 1. What is the probability that San Francisco plays in the next Super Bowl?1 solutions Answer 134122 by edjones(7569)   on 2009-01-29 11:51:36 (Show Source): You can put this solution on YOUR website!Let p be the probability that they play. Let n be the probability that they don't. . p=9n p+n=1 . 9n+n=1 Substitute for p. 10n=1 n=.1 p=.9 . Ed
 Expressions-with-variables/179115: (6)/(x-2)+(7)/(x-7)=(7)/(x^2-9x+14)1 solutions Answer 134082 by edjones(7569)   on 2009-01-29 00:49:38 (Show Source): You can put this solution on YOUR website!(6)/(x-2)+(7)/(x-7)=(7)/(x^2-9x+14) 6/(x-2) + 7/(x-7) = 7/(x-7)(x-2) 6(x-7)+7(x-2)=7 Multiply each side by (x-7)(x-2). 6x-42+7x-14=7 13x=63 x=63/13 . Ed
 Permutations/179123: This question is from textbook Permutation and Combinations Please you help me fins this problem How do you know? 15.) What if...? In the United Kingdom's National Lottery, you must correctly select a group of 6 numbers from 49. Suppose that the contest were changed to selecting 7 numbers. How many more ways would there be to select the number? Please rely me back as soon as you could. Thank you.1 solutions Answer 134079 by edjones(7569)   on 2009-01-29 00:32:08 (Show Source): You can put this solution on YOUR website!49C6=13983816 49C7=85900584 49C7-49C6=71,916,768 Answer . Ed
 Expressions-with-variables/179124: I was wondering how to show my work on a problem when x-11=5x+151 solutions Answer 134077 by edjones(7569)   on 2009-01-29 00:23:28 (Show Source): You can put this solution on YOUR website!x-11=5x+15 -4x=26 Add -5x+11 to each side. x=26/-4 =-6.5 . Ed
 Probability-and-statistics/178525: I need help with this Question? 5.62 A certain airplane has two independent alternators to provide electrical power. The probability that a given alternator will fail on a 1-hour flight is .02. What is the probability that (a) both will fail? (b) Neither will fail? (c) One or the other will fail? Show all steps carefully. 1 solutions Answer 133481 by edjones(7569)   on 2009-01-26 01:30:22 (Show Source): You can put this solution on YOUR website!.02*.02=.0004 Both will fail .98^2=.9604 Neither will fail. .02+.02=.04 One or the other will fail. . Ed
 Average/178518: Maria averaged 212 miles on the first 3 days of her trip. she averaged only 104 miles on the last 6 days of her trip. What was the overall average number of miles driven per day?1 solutions Answer 133478 by edjones(7569)   on 2009-01-26 01:08:58 (Show Source): You can put this solution on YOUR website!212*3=636 104*6=624 _________ =====>1260 . 1260/9=140 mi/day average. . Ed
 percentage/178528: what is 12 percent of 2,7001 solutions Answer 133476 by edjones(7569)   on 2009-01-26 00:59:28 (Show Source): You can put this solution on YOUR website!12%=.12 2700*.12=324 . Ed
 Numbers_Word_Problems/177956: h = vt - 16t^2 solve for v1 solutions Answer 132921 by edjones(7569)   on 2009-01-22 14:29:27 (Show Source): You can put this solution on YOUR website!h = vt - 16t^2 solve for v h-vt=-16t^2 -vt=-16t^2-h v=-(16t^2+h)/-t =16t+(h/t) . Ed