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# Recent problems solved by 'richard1234'

richard1234 answered: 5385 problems
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 decimal-numbers/488017: DESCRIBE TWO METHODS FOR DETERMINING WHERE TO PLACE THE DECIMAL POINT IN THE PRODUCT OF TWO DECIMALS?1 solutions Answer 333281 by richard1234(5390)   on 2011-08-30 00:31:28 (Show Source): You can put this solution on YOUR website!Method #1 is when you are multiplying two decimal numbers, count how many digits are after the decimal point for each number. For example, (36.58)(2.4), there are two digits after the decimal point in 36.58 and one digit for 2.4. Add these to get three, so after you multiply, move the decimal point three positions to the left to compensate. Method #2 is intuition (because 36.58 times 2.4 can't equal 877.92 can it?). There's really only one method (and maybe variations) to find where to put the decimal point, though.
 Triangles/488140: If two triangles have the same perimeter, how do I find the dimensions?1 solutions Answer 333272 by richard1234(5390)   on 2011-08-30 00:14:06 (Show Source): You can put this solution on YOUR website!Not enough information.
 Angles/488137: if m1 solutions Answer 333268 by richard1234(5390)   on 2011-08-30 00:05:31 (Show Source): You can put this solution on YOUR website!Where are points A,C,B,D in relation to each other?
 Numbers_Word_Problems/488142: How can I find all sets of three consecutive integers whose sum is between 30 and 40?1 solutions Answer 333267 by richard1234(5390)   on 2011-08-30 00:02:18 (Show Source): You can put this solution on YOUR website!{9,10,11},{10,11,12},{11,12,13},{12,13,14}. ({13,14,15} doesn't work) Just eyeball it, roughly approximate by dividing by 3 and you can find all such sets.
 test/488158: 1,2 4,6 what are the next 3 sets of numbers1 solutions Answer 333266 by richard1234(5390)   on 2011-08-29 23:53:17 (Show Source): You can put this solution on YOUR website!You want the next three numbers, not the next three sets of numbers. Even then, your sequence is not very well defined.
 Graphs/487974: f(x)=2x^2-9x+7 How do I solve for x here? 1 solutions Answer 333220 by richard1234(5390)   on 2011-08-29 18:54:05 (Show Source): You can put this solution on YOUR website!You can find the roots of x by applying by the quadratic formula, but you can't solve for a numerical value of x unless you set f(x) equal to something (e.g. 0).
 Trigonometry-basics/487970: how do you solve tanx/x i can't quite figure it out.1 solutions Answer 333219 by richard1234(5390)   on 2011-08-29 18:46:27 (Show Source): You can put this solution on YOUR website!You can't "solve" it as you might solve an equation. You can graph it or find its derivative or something but you can't "solve" tan(x)/x.
 Systems-of-equations/487953: How do I solve for X: ax+bx=c1 solutions Answer 333217 by richard1234(5390)   on 2011-08-29 18:38:21 (Show Source): You can put this solution on YOUR website!Factor LHS x(a+b) = c, divide both sides by a+b. x = c/(a+b)
 test/487933: How do you differentiate the properties associative,communitive, and distributive 1 solutions Answer 333215 by richard1234(5390)   on 2011-08-29 18:36:09 (Show Source): You can put this solution on YOUR website!For any binary operation * (not necessarily addition or multiplication): * is said to be associative if (a*b)*c = a*(b*c) for all a,b,c ∈ S (S is a set composed of all possible a,b,c) * is said to be commutative if a*b = b*a for all a,b ∈ S * is said to be distributive over another operation (I'll denote this operation by &) if a*(b&c) = (a*b)&(a*c) for all a,b,c ∈ S. For example, vector addition is commutative and associative, scalar products are distributive, the dot product of vectors is commutative, and the cross product of vectors is associative over vector addition, but not commutative (in fact, it is said to be anti-commutative, similar to subtraction). These are just examples of operations other than addition or multiplication that obey these properties.
 Miscellaneous_Word_Problems/487606: a right cylinder is inscribed in a sphere of radius 10.express its volume and surface area as functions of its height,h.1 solutions Answer 333214 by richard1234(5390)   on 2011-08-29 18:28:31 (Show Source): You can put this solution on YOUR website!Assume the radius of the cylinder is r. Upon drawing the sphere and cylinder, draw a right triangle (with a vertex at the center of the sphere) with legs r and h/2, and hypotenuse 10 (since the distance from the center to the edge of the sphere is 10). This will satisfy the Pythagorean theorem Now use the volume and surface area formulas: and replace your expression for r into each of these.
 Proportions/487594: a. (9-5)-(6-8)= b. Which expression has the smallest value (-4), (-8), (7) or (16)? Thank you so much!1 solutions Answer 333212 by richard1234(5390)   on 2011-08-29 18:23:02 (Show Source): You can put this solution on YOUR website!a. Do the operations in parentheses first...e.g. 9-5 = 4, 6-8 = -2. Then (9-5)-(6-8) = 4-(-2) = 4+2 = 6. b. -8 is the smallest of the four numbers.
 Sequences-and-series/487949: How do you do the problem n=19 an=155 and d=8? in arithmetic sequence1 solutions Answer 333211 by richard1234(5390)   on 2011-08-29 18:21:40 (Show Source): You can put this solution on YOUR website!You can't "do" a certain arithmetic sequence; you have to explain what "do" means. If a sequence is denoted a_1, a_2, ..., a_n, ... and n = 19, then a_19 denotes the 19th term of the sequence. d=8 is the common difference; i.e. each term in the sequence is 8 more than the previous one. a_n = 155 means the nth term is 155. You'll have to rephrase your problem for it to make more sense and obtain an answer.
 Average/487750: Respected Sir , Please help me to solve this question, I will be very grateful for your help If a variable assumes the value 1,2,3.....5 with frequencies as 1,2,3,....5, then what is the AM ? As the answer given is : 11/3 Please help me to simplify this !!! 1 solutions Answer 333209 by richard1234(5390)   on 2011-08-29 18:18:46 (Show Source): You can put this solution on YOUR website!You want to find the arithmetic mean of one 1, two 2's, ..., five 5's, which is essentially since the sum of the entries is 1^2 + ... + 5^2 and there are 1+2+...+5 entries.
 Rectangles/487906: Rectangle with 4 m base 2 and height 2 cm1 solutions Answer 333208 by richard1234(5390)   on 2011-08-29 18:16:47 (Show Source): You can put this solution on YOUR website!What is the extra 2 doing there? Hopefully the height is not 4 meters in base 2, which would be meaningless and incorrect. Even then, what would you want to do with such a rectangle?
 Quadratic_Equations/487283: Help ASAP please! The point is on the graph of y=-x^2+kx-4. What is the value of k?1 solutions Answer 333088 by richard1234(5390)   on 2011-08-29 00:01:38 (Show Source): You can put this solution on YOUR website!What point?
 Equations/487120: which of the following could be the units digit of 57^n where n is a positive integer? Indicate all such digits: A.) 0 B.) 1 C.) 2 D.) 3 E.) 4 F.) 5 G.) 6 H.) 7 I.) 8 J.) 9 1 solutions Answer 333087 by richard1234(5390)   on 2011-08-29 00:01:08 (Show Source): You can put this solution on YOUR website!Same units digits as 7^n. 7^1 ≡ 7 (mod 10), 7^2 ≡ 9, 7^3 ≡ 3, 7^4 ≡ 1, 7^5 ≡ 7, and the pattern repeats. The only possible digits are 1,3,7,9.
 Probability-and-statistics/487164: a set of data is normally distributed with a mean of 200 and standard deviation of 50. what would be the standard score for a score of 3001 solutions Answer 333086 by richard1234(5390)   on 2011-08-28 23:58:16 (Show Source): You can put this solution on YOUR website!The z-score would be 2, since it is two standard deviations above the mean.
 Linear_Algebra/487600: How do I find the x and y intercepts? Help. Do I have to guess at the numbers? Find the x- and y-intercepts for the equation 4x – 3y = 9. Please show all of your work. Then graph the equation. 1 solutions Answer 333085 by richard1234(5390)   on 2011-08-28 23:56:32 (Show Source): You can put this solution on YOUR website!No guessing...to find the x-intercept, set y equal to zero and solve for x. Similarly, to find the y-intercept, set x equal to zero and solve for y.
 Linear_Algebra/487277: Пlease help me with those questions!!! 1. Find all triples (x; y; z) of positive integers such that x < y < z and (1/x)-(1/xy)-(1/xyz)=19/9 2. Show that from any five integers, one can always choose three of these integers such that their sum is divisible by 3. Thank you very much!!! 1 solutions Answer 333084 by richard1234(5390)   on 2011-08-28 23:55:46 (Show Source): You can put this solution on YOUR website!1. There are none. Since x < y < z, the maximum value of the LHS is about 1 (set x = 1, y,z to be large numbers). The LHS can never get larger than 1, so there are no solutions (x,y,z) of positive integers. 2. Out of any five integers, there will either exist an integer for each residue modulo 3 (in which we're done), or all five integers will occupy two different residues mod 3. If this is the case, then by a simple Pigeonhole argument, three of them have the same residue mod 3, in which we're also done (since the sum of these three is 0 mod 3).
 Expressions-with-variables/487206: what is the varible expression the sum of b and 4 1 solutions Answer 333083 by richard1234(5390)   on 2011-08-28 23:43:39 (Show Source): You can put this solution on YOUR website!b+4
 Number-Line/487257: simplify. show all of the steps to arrive at your answers (18)(-18)+30(-16)1 solutions Answer 333082 by richard1234(5390)   on 2011-08-28 23:43:01 (Show Source): You can put this solution on YOUR website!18(-18) = -324 30(-16) = -480 18(-18) + 30(-16) = -324 + (-480) = -804
 Square-cubic-other-roots/487442: Sum of 2819 Sum of 40031 solutions Answer 333081 by richard1234(5390)   on 2011-08-28 23:40:29 (Show Source): You can put this solution on YOUR website!Sum of 2819? Addition is a binary operation, so you need two numbers.
 real-numbers/487382: It says : Name the set(s) of numbers to which each number belongs. Solve 1.931 solutions Answer 333080 by richard1234(5390)   on 2011-08-28 23:38:57 (Show Source): You can put this solution on YOUR website!You didn't specify which "sets." Assuming you mean the "double-stroke" sets i.e. real, rational, integer, whole number, natural number, 1.93 is a real number and a rational number (193/100) but not an integer.
 Quadratic_Equations/487494: Explian the four steps for solving quadratic equations? Can any of these steps be eliminated? Can the order of the these steps be changed? Would you add any steps to make it easier,or to make it easier to understand?1 solutions Answer 333079 by richard1234(5390)   on 2011-08-28 23:36:26 (Show Source): You can put this solution on YOUR website!Either complete the square or factor. If neither of these work very well, you can use the quadratic formula. But you only need to use one method (as long as you do your arithmetic correctly). As to eliminating/adding steps, there is no need to do so, and no need to change the steps. I can't really answer those questions; you'll learn much better by practicing solving quadratic equations.
 Equations/487475: When is a variable a solution to an equation?1 solutions Answer 333078 by richard1234(5390)   on 2011-08-28 23:31:53 (Show Source): You can put this solution on YOUR website!If the number that the variable represents satisfies the equation (i.e. you get an equality or true equation).
 Rectangles/487560: Lenght of a rectangle is 1 unit more than it's width. The area of this rectangle is 30 square units. What are the dimensions of the rectangle1 solutions Answer 333077 by richard1234(5390)   on 2011-08-28 23:29:40 (Show Source): You can put this solution on YOUR website!5 units by 6 units. You can do this by noting that 30 = 5*6, or by doing it the longer way by letting x(x+1) = 30 and solving via factoring.
 Graphs/487575: y = -3/4x-6 what is y if x is 8? what is x if y is 6? what is y if x is 0? what is x if y is -9? what is y if x is -4? what is x if y is 0?1 solutions Answer 333076 by richard1234(5390)   on 2011-08-28 23:28:45 (Show Source): You can put this solution on YOUR website!Just plug in the variable that is known and solve for the other number. For example, "what is y if x is 8?" Just replace x = 8 to get y = (-3/4)(8) - 6 = -12. Do the others the same way.
 Angles/487590: Give an exact value for sin(5pi/6 radians) don't just solve the problem explain to me how you did it! Thank you1 solutions Answer 333075 by richard1234(5390)   on 2011-08-28 23:26:00 (Show Source): You can put this solution on YOUR website!sin(5pi/6) = 1/2. Just find 5pi/6 on a unit circle and find the y-coordinate (using 30-60-90 triangles).
 Functions/487591: how is this true 5+4+3+3+3+3+4+3+4=(-4)? you cannot change anything or add anything to make the problem true1 solutions Answer 333074 by richard1234(5390)   on 2011-08-28 23:22:42 (Show Source): You can put this solution on YOUR website!Is 32 equal to -4?
 Angles/487586: supplement of angle B if B equals 2x-4. I just need a reminder on how to solve.1 solutions Answer 333073 by richard1234(5390)   on 2011-08-28 23:14:04 (Show Source): You can put this solution on YOUR website!Just subtract that number from 180 to get 180 - (2x - 4) = 180 - 2x + 4 = 184 - 2x.
 Geometry_Word_Problems/487566: i need to find the counterexample to this conjecture: All rectangles with a perimeter of 20ft have the same area. note: perimeter= 2(Length+Width)1 solutions Answer 333072 by richard1234(5390)   on 2011-08-28 23:01:13 (Show Source): You can put this solution on YOUR website!There are lots of counterexamples, so you do not need to refer to it as "the counterexample." For example, a 4 ft * 6 ft rectangle and a 3 ft * 7 ft rectangle both have perimeter 20 ft, but their areas are different (24 ft^2 vs. 21 ft^2).