Model Sum - P3

by Theresa
(Singapore)

My answer is 18 however the answer provided was 54. Please advise where I miss.


There are twice as many books in Box A than Box B. When some books are moved from Box A to Box B, the number
of books in Box B is 5 times as many as Box A. If there are 72 books in Box A at first, how many books are there left
in Book A in the end?

Zach's Answer:

Hi Theresa,

Your answer is correct, it should be 18. For the answer to be 54, the question should read "How many books are moved from Box A to Box B?" Let me know if you have further questions.

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Feb 02, 2015
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First try
by: Alfie

A has 2 big blocks, B has 1 big block.
Divide the big blocks into 2.
A has 4 small blocks, B has 2 small blocks.
Move 3 small blocks from A to B.
So now B has 5 small blocks and A has 1 small block, fulfilling the requirements of the question. Now, 1 small block is 72/4 = 18

Aug 15, 2013
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Answer to the above question
by: Ms. Thaslim

Box A has twice as many books as box B. so,
B = 72/2 = 36
when some books are transferred to from box A to B, B has five times the books as in A. So we get 6 units totally. 1 for A and 5 for B (since B has 5 times the amount as in A).Therefore

A + B = 72+ 36 = 108
1 unit = 108 / 6 = 18
Thus Box A has 18 books at the end.

P.S sorry,I couldn't type-draw the block diagram in here.


Oct 01, 2012
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Please explain the solution
by: Kumar

Hi Zach,

Can you please explain the solution

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