Mrs. lee baked 3 times as many curry puffs as apple pies. after giving away 30 curry puffs, she had twice as many apple pies as curry puffs. how many curry puffs did she bake?

  36

Step-by-step explanation:

Let c represent the number of curry puffs Mrs. Lee baked. Then the given relationship can be modeled by ...

  (c-30)/(c/3) = 1/2 . . . . . the ratio of curry puffs to pies after giving away 30

  2(c -30) = c/3 . . . . . . . cross multiply

  6(c -30) = c . . . . . . . . . multiply by 3

  5c -180 = 0 . . . . . . . . . eliminate parentheses, subtract c

  c -36 = 0 . . . . . . . . . . . divide by 5

  c = 36 . . . . . . . . . . . . . .add 36

Mrs. Lee baked 36 curry puffs.

This answer format requires that we put the answer first. In order to do that, we often must solve the problem before we write the explanation. Sometimes, this can be done using a simple strategy that may not be the easiest to explain, and may not correspond to anything you study in your curriculum materials.

Here, we can write the initial ratio of puffs to pies as ...

  puffs : pies = 3 : 1

After 30 puffs are given away, the ratio is

  (puffs -30) : pies = 1 : 2

If we multiply the initial ratio by 2, we can write ...

  puffs : pies : (puffs-30) = 6 : 2 : 1

That is, giving away 30 puffs dropped its "ratio unit" count from 6 to 1, so those 30 puffs must represent 5 ratio units. Then the initial 6 ratio units of puffs will be 6·(30/5 puffs) = 36 puffs.