Rutgers/Lucent ALLIES IN TEACHING MATHEMATICS AND TECHNOLOGY Grant
Using technology not simply to do things better, but to do better things.


INCORRECT STUDENT RESPONSES:
Eminem and Elton


Answer #1: She sold 46 Did with brother Dawid Dabrowski
Explanation: I set up 3 formulas.
Monday---> 80-n=x. she put out 80 copies in the morning and then she sold a certain number (n) and came up with a number left on the shelf (x).
Tuesday---> 2x-n=f. she doubled the number of copies left on the shelf from monday so i put 2 times (x) and then subtracted the amount she sold on monday (n) and came out with (f) or the number of copies left on the shelf at the end of tuesday.
Wednesday---> 3f-n=0. on wednesday she tripled the amount left from tuesday so i multiplied (f) by 3. Then at the end of the day she saw that she sold the same amount as she did on the 2 previous days so i subtracted (n) again and equaled that to zero because there was none left on the shelf at the end of wednesday.
n= # of copies sold each day
x= # of copies left on monday
f= # of copies left on tuesday

After this i used try and check a few times until i narrowed the answer to be in between 45 and 51. After using try and check again i came up on 48. I plugged it in the first formula as n. So, 80-48=32. s (x) now equals 32. Then i transferred these numbers into the variables of the second formula. 2(32)-48=f which then translates into 64-48=16. so (f) equals 16. then i took my variables and plugged them into the 3rd formula. 3(16)-48=0 which turns into 48-48=0. So she sold 48 copies on monday, tuesday, and wednesday.


Answer #2: She sold 20 copies of DVd's per day
Explanation: OK what I did was gather all the information. It was said that on Monday there were 80 copies on the shelf and by the end of the day some were sold. Then the store decided to double the amount of c.d.'s and on Tuesday they had the same amount as on Monday. So she had to sell 20 c.d's on MOnday to reduce the number of c.d's to 40. 40 x 2=80. Then on Wednesday the manager decided to triple the amount of c.d's. However, she sold the same number of c.d;s on Wednesday then on the other days. So if they tripled the number of c.d's and still end up getting 80 just like the other days then less c.d's would have to be on the stack after Tuesday. So after Tuesday there should have been about 76 c.d's on the stack and then mulitplying it by 3 will give us about 80 c.d's. So from there i concluded that 20 dvd's were being sold each day.


Answer #3: 24
Explanation: first i gave each day an equation as follows :
monday = (80 - x)
tuesday = (2(80 - x) - x = 160 - 3x
wednesday = {3(2(80 - x) - x} =
then i put them all into one equation and set it equal to zero and then solved for x.
80


Answer #4: The manager of The Hip Hop Shop sold 48 copies each day.
Explanation: I started with 80 because she started with 80. Then i sutracted 46 from 80 and got 34 then i times 34 times 2 and got 68 then i subtracted 46 and got 22 times that by 3 and got 66 subtracted 46 and got the answer of 20 then i divided 3 into 20 got the answer of 6 point something and i divided that into 3 again and got 2 so i added 2 to 46 and got the answer of 48.


Answer #5: She sold 48 copies each day.
Explanation: I used a guess and check stratagy until I came up with an answer that made the CD's left equal zero. 80-48=32 32+32=64 64-48=16 16*3=48 48- 48=0


Answer #6: She sold 48 copies each day.
Explanation: I used a guess and check stratagy until I came up with an answer that made the CD's left equal zero.
80-48=32
32+32=64
64-48=16
16*3=48
48-48=0

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