In September, Julian gave his wife, Usha, $8000 for household expenditure. Usha spent 50% of the sum on rental, 20% on food and saved the rest. In October, Julian reduced the sum he gave to Usha. Usha 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 October. By what percentage was the sum given to Usha reduced by?

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

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

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

Total amount that Julian 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 Julian spent on rental and food is repeated. 

80 u = 68% 

80 u = 5440

1 u = 5440 ÷ 80 = 68

Amount that Julian gave to Usha in October
= 100 u
= 100 x 68
= $6800

Amount that Usha received less from Julian from September to October
= 8000 - 6800
= $1200

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

Answer(s): 15%