math problem, please explain it for me.?

Question

during a sale at an office supply store, for every box of paper clips purchased for 15 cents, a second box can be purchased for 4 cents. How many boes of paper clips did Paul buy if he spent 91 cents on boxes of paper clips?
A.6 B.7 C.8 D.9 E.10
PLEASE explain this problem, since the total cost is 91, it is impossible to look reasonable. please tell me your idea on this problem.

Answer 1

The sneaky explanation is that "a second box CAN be purchased", but not that "a second box MUST be purchased".

So he bought some boxes at 15 cents, and the same number or fewer boxes at 4 cents. We start at 91 cents and subtract 4 cents per box until we get to a whole multiple of 15 cents, then hope that the box counts come out the right way round.

91, 87, 83, 79, 75 - whoa! So four 4-cent boxes leaves 75 cents that Paul spent on 15-cent boxes, five of them. Phew, five is more than four, so the answer D (5 + 4 = 9) is okay.

If Paul spent 27 cents, that would be impossible, because he can't get three 4-cent boxes with only one 15-cent box. But as the problem is given, there is an answer which works. It doesn't explain why Paul didn't take up a fifth box at 4 cents, but they don't ask that.

Answer 2

Allright so he ends up spending 91 cents.

15 cents + 4 cents = 19 cents

19x5= 95 cents (too much) that would be 10 boxes

95 cents - 4 cents = 91 cents (the amount you want) and since it was the second box it would have been 4 cents

Answer: 9 Boxes of paper clips

Answer 3

two boxes together costs 19 cents.

91 / 19 = 4.78 so you can only have 4 sets of 2 boxes

4 x 19 = 76 and you still have some money left over

91 - 76 = 15 cents to buy the last box.

So all together you have 4 sets of 2 boxes plus the last box.

= 9 boxes

Answer 4

Now, math is not my strong suit, but I think it is like this: he buys four times a 15 cent and a 4 cent box. then he has spent 76 cents ( 4 times 15 and 4 times 4 ) then he needs to spend another 15 cents to make it 91. so he has bought 9 boxes. (only the last time he doesn't buy the 4 cent box... i think.... ) answer D.

Answer 5

Simple - We purchased as many as the store had -
15 + 4 = 19 cents = 2
38 = 4
76 = 8 - - - - - - BUT they only had one left in stock
+15

========= 91 cents -- - - - --we bought 9

Answer 6

9

Answer 7

group the first two boxes as a set: 4+15=19cents for 2 boxes.

91/19=4.789

thus Paul will have bought 4 sets, and remainder is 91 - (19x4) = 15cents
-->just nice for another box.

therefore: total number of boxes = 4x2 + 1 = 9
ans: D

Answer 8

It means that 4.7 is in two brackets, the 2 )) at the end is the closing part of the two brackets because as you know (hopefully) all brackets begin with "(" and end with ")". There is a negative sign in front of a bracket. Think of each - sign as a -1, since multiplying by 1 doesn't change the value then... -(-(-4.7)) = -1(-1(-4.7)) When a number is in front of a bracket it always means multiply (remember that) so that means... -1(-1(-4.7)) = -1*-1*-4.7 Then you can just use multiplication to figure it out!

Answer 9

15 + 4 = 19
91 / 19 = your answer