# Question

Tom has \$420 more than Jerry at first. For every @2 Tom saves, Jerry saves \$5. Find the amount of money Jerry has saved when Jerry and Tom have the same amount of money.

I know that the answer is to get the difference of 5-2=3. then take 420/3=140, followed by 140×5=700. Answer is \$700. I’m not sure how this steps can be explained to my child. Especially, the part where 140×5….Please help.

Thanks.

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1 cycle = Tom saves \$2 and Jerry saves \$5 (\$3 more than Tom)

It takes \$420 / \$3 = 140 cycles of the above for Jerry to catch up with Tom

Hence, Jerry saved 140 cycles of \$5 = \$700

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5 – 2 = 3 (Jerry saves \$3 more for every \$2 Tom saves)
420/3 = 140 (Jerry saves \$5 140 times = Tom saves \$2 140 times + 420 as shown next)
140 x 5 = 700 or 420 + 140 x 2 = 700

Ans : \$700.

Note : I use “times’ as the question did not mention “days”.

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How about changing the question slightly to

“Everyday, Tom saves \$2, while Jerry saves \$5.”

420 ÷ 3 = 140 will be the number of days saved before the excess of \$420 was depleted.

So after 140 days, Jerry would have saved 140 × 5 = \$700

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