Tommy had $227 and Ken had $185 at first. Each of them bought an identical cardigan and an identical skirt from the same shop. The skirt cost 3 times as much as the cardigan. In the end, Tommy had 3 times as much money as Ken. What was the cost of the cardigan?

	Tommy	Ken	Difference
Before	$227	$185	$42
Change	- 1 cardigan - 1 skirt	- 1 cardigan - 1 skirt
After	3 u	1 u	2 u

Since Tommy and Ken bought the same items, the difference  in their amounts remains the same.

Difference in the amounts that they had
= 3 u - 1 u
= 2 u

2 u = 227 - 185
2 u = 42

1 u = 42 ÷ 2 = 21

Amount that Ken had in the end
= 1 u
= $21

Cost of 1 cardigan and 1 skirt
= 185 - 1 u
= 185 - 21
= $164

The skirt cost 3 times as much as the cardigan.

Cost of 1 cardigan = 1 p
Cost of 1 skirt = 3 p

Total cost of 1 cardigan and 1 skirt
= 1 p + 3 p
= 4 p

4 p = 164

1 p = 164 ÷ 4 = 41

Cost of the cardigan
= 1 p
= $41

Answer(s): $41