If Cindy gives Paul $36, the amount of money she has will be 40% of his. If Paul gives Cindy $36, he will have the same amount of money as her. How much money did each of them have?
(a) Paul
(b) Cindy

	Case 1		Case 2
	Paul	Cindy	Paul	Cindy
Before	5 u - 36	2 u + 36	3.5 u + 36	3.5 u - 36
Change	+ 36	- 36	- 36	+ 36
After	5 u	2 u	3.5 u	3.5 u

(a)
40% = ⁴⁰₁₀₀ = ²₅

In Case 1, when Cindy gives to Paul, there is an internal transfer of money from Cindy to Paul.  The total amount that both have remains the same.

In Case 2, when Paul gives to Cindy, there is an internal transfer of money from Paul to Cindy. The total amount that both have remains the same.

The total amount that both have in Case 1 and Case 2 are the same.

Total amount that Cindy and Paul have
= 5 u + 2 u
= 7 u

Amount that Cindy and Paul each has in the end for Case 2
= 7 u ÷ 2
= 3.5 u

Amount that Paul has at first is the same in Case 1 and Case 2.

5 u - 36 = 3.5 u + 36
5 u - 3.5 u = 36 + 36
1.5 u = 72 

1 u = 72 ÷ 1.5 = 48

Amount that Paul has
= 5 u - 36
= 5 x 48 - 36
= 240 - 36
= $204 

(b)
Amount that Cindy has
= 2 u + 36
= 2 x 48 + 36
= 96 + 36
= $132

Answer(s): (a) $204; (b) $132