Grade 4 - Progress in Mathematics

Karl bought some guppies in March.

He had four times as many guppies

by the end of M ay. He had 46 guppies

by the end of June, which was

10 more than at the end of M ay. How

many guppies did he buy in March?

Problem-Solving Strategy:

Work Backward

4-15

Work backward. Use the inverse operation.


First, find the number of guppies at the end of May:

Subtract 10 from the number of guppies he had in June.

46 
 10 number in May


Then find the number of guppies he had in March:

Divide the number of guppies in May by 4.

number in May  4 number in March

Start with 9. Use the inverse operation.

9 guppies in March

9  4 36 in May

36  10 46 in June The answer checks.

Visualize the facts of the problem as you reread it.

Facts: Karl bought guppies in March.

4 times as many in May

10 more than that in June

46 guppies in June

Question: How many guppies did Karl buy in March?

46 
 10  36 number in May

36  4  9 number in March

Karl bought 9 guppies in March.

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