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 10-13-2012, 04:01 PM #256 Junior Member   Join Date: Apr 2011 Posts: 83 If (x + y) (x^2 - y^2) = 0 , which of the following must be true? (A) x = y (B) x = -y (C) x^2 = y^2 (D) x^2 = -y^2 (E) x^3 = x^3 C is the correct answer, but what makes B more incorrect than C? This was the final question on section 2 of the 2006 Saturday PSAT. Reply
 10-13-2012, 04:22 PM #257 Senior Member   Join Date: Mar 2012 Location: Cambridge, MA Posts: 1,913 B is incorrect because x could equal y, therefore B does not have to be true. Here, x^2 = y^2, or x = +/- y, answer is C. Reply
 10-22-2012, 09:57 PM #258 New Member   Join Date: Jan 2012 Posts: 11 a train started at station s and has been traveling r miles per hour for t hours in terms of r and t ,how many miles from station had the train travled 3t/4 hours ago ? the answers is (E) i cannot understand why it is e Reply
 10-22-2012, 10:00 PM #259 Junior Member   Join Date: Mar 2012 Posts: 88 ^ would be helpful to list answer choices, (esp. E). I assume the answer goes something like this: at 3t/4 hours ago, the train has traveled for t-3t/4 or t/4 hours, so distance = rate * time, so distance = r * t/4 = rt/4 miles from station. Reply
 10-22-2012, 10:37 PM #260 New Member   Join Date: Jan 2012 Posts: 11 thanks for your help Last edited by SalmaThabet; 10-22-2012 at 10:45 PM. Reply
 10-23-2012, 08:26 PM #261 New Member   Join Date: Jan 2012 Posts: 11 three children each weight 100 pounds or less their averge (arithmetic mean ) weight is 80 pounds if one of them weighs 80 pounds , what is the least possible weight , in pounds,of a child in the group? the answers is 60 Reply
 10-23-2012, 09:07 PM #262 Senior Member   Join Date: Jun 2011 Location: ~West Coast Bound~ Posts: 1,023 Explanation: The total of their weights are 240. [(x+y+z)/3=80]->[x+y+z=240] One of the kids weigh 80 lbs. [240-80=160] Find the smallest number x could be. [160-100=60]{The largest weight a child could be} Gives you the smallest weight. 60 lbs. Reply
 10-23-2012, 10:07 PM #263 New Member   Join Date: Jun 2012 Location: Rhode Island Posts: 26 If a-x =12, b-y=7, c-z=15, and a+b+c=50, then x+y+z=? Answer is 16. How do you solve this? Please and thank you! Reply
 10-23-2012, 10:18 PM #264 Senior Member   Join Date: Jun 2011 Location: ~West Coast Bound~ Posts: 1,023 It's plain old substitution:a=12+x b=7+y c=15+z Plug it into a+b+c=50 (12+x)+(7+y)+(15+z)=50 Then you get: x+y+z=16 Reply
 10-23-2012, 10:26 PM #265 New Member   Join Date: Jan 2012 Posts: 11 a-x=12 then a=12+x ,b-y=7 then b=7+y and c-z=15 then c=15+z , 12+x+7+y+15+c=50 12+7+15=34 34+x+y+z=50 x+y+z=50-34=16 Reply
 10-23-2012, 10:30 PM #266 New Member   Join Date: Jan 2012 Posts: 11 1)a person paid atotal of \$700 for shirts priced at \$ 9 and \$ 13 each if the person purchased two \$ 13 shirts for every \$ 9 shirt , what was the total number of shirts purchased? 2)if 1 jar +5 cups =1 tub and if 3 jars +2 cups =2 tubs, how many cups equal a tub ? the answers of the first 60 and the secound 13 Reply
 10-23-2012, 10:48 PM #267 New Member   Join Date: Jan 2012 Posts: 11 i know the secound question please help me to solve the first Reply
 10-23-2012, 11:53 PM #268 Junior Member   Join Date: Mar 2012 Posts: 88 let a = \$9 shirts, then there are 2a \$13 shirts because he bought two \$13 shirts for each \$9 shirt 13(2)a + 9a = 700 35a = 700 a = 20 TOTAL SHIRTS = a + (2)a = 3a = 60 Reply
 10-25-2012, 03:28 PM #269 New Member   Join Date: Jun 2012 Location: Rhode Island Posts: 26 Thanks for the help! Greatly appreciated!! Reply
 10-30-2012, 07:35 PM #270 New Member   Join Date: Jan 2012 Posts: 11 in a discount clothing store, Billie bought 4 pairs of socks at x dollars per pair and 3 shirts at 3x dollars each. if the total cost of the socks and shirts was \$ 19.50, what was the cost, in dollars,of one shirts ? the answer is 450 Reply

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