In July, Charlie gave his wife, Lynn, $4000 for household expenditure. Lynn spent 50% of the sum on rental, 20% on food and saved the rest. In August, Charlie reduced the sum he gave to Lynn. Lynn spent the same amount on rental and reduced the amount she spent on food by 20%. She saved the remaining 20% of the sum given to her in August. By what percentage was the sum given to Lynn reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$4000
Change		- 4%	- ?	- ?
After	50%	16%
Comparing the amounts spent in August	80 u		20 u	100 u

Amount that Charlie saved in percent
= 100% - 50% - 20%
= 30%

Amount that Charlie reduced on food in percent
= 20% x 20%
= ²⁰₁₀₀ x 20
= 4%

Total amount that Charlie spent on rental and food in percent
= 50% + 16%
= 66%

100% → 4000

1% → 4000 ÷ 100 = 40

66% → 66 x  40 = 2640

The total amount that Charlie spent on rental and food is repeated. 

80 u = 66% 

80 u = 2640

1 u = 2640 ÷ 80 = 33

Amount that Charlie gave to Lynn in August
= 100 u
= 100 x 33
= $3300

Amount that Lynn received less from Charlie from July to August
= 4000 - 3300
= $700

Percentage that the sum given to Lynn was reduced by from July to August
= ⁷⁰⁰₄₀₀₀ x 100%
= 17.5%

Answer(s): 17.5%