In August, Cole gave his wife, Winnie, $8000 for household expenditure. Winnie spent 50% of the sum on rental, 20% on food and saved the rest. In September, Cole reduced the sum he gave to Winnie. Winnie spent the same amount on rental and reduced the amount she spent on food by 10%. She saved the remaining 20% of the sum given to her in September. By what percentage was the sum given to Winnie reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$8000
Change		- 2%	- ?	- ?
After	50%	18%
Comparing the amounts spent in September	80 u		20 u	100 u

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

Amount that Cole reduced on food in percent
= 10% x 20%
= ¹⁰₁₀₀ x 20
= 2%

Total amount that Cole spent on rental and food in percent
= 50% + 18%
= 68%

100% → 8000

1% → 8000 ÷ 100 = 80

68% → 68 x  80 = 5440

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

80 u = 68% 

80 u = 5440

1 u = 5440 ÷ 80 = 68

Amount that Cole gave to Winnie in September
= 100 u
= 100 x 68
= $6800

Amount that Winnie received less from Cole from August to September
= 8000 - 6800
= $1200

Percentage that the sum given to Winnie was reduced by from August to September
= ¹²⁰⁰₈₀₀₀ x 100%
= 15%

Answer(s): 15%