In July, Zeph gave his wife, Min, $9000 for household expenditure. Min spent 60% of the sum on rental, 30% on food and saved the rest. In August, Zeph reduced the sum he gave to Min. Min spent the same amount on rental and reduced the amount she spent on food by 30%. She saved the remaining 10% of the sum given to her in August. By what percentage was the sum given to Min reduced by?

	Rental	Food	Savings	Total
Before	60%	30%	10%	$9000
Change		- 9%	- ?	- ?
After	60%	21%
Comparing the amounts spent in August	90 u		10 u	100 u

Amount that Zeph saved in percent
= 100% - 60% - 30%
= 10%

Amount that Zeph reduced on food in percent
= 30% x 30%
= ³⁰₁₀₀ x 30
= 9%

Total amount that Zeph spent on rental and food in percent
= 60% + 21%
= 81%

100% → 9000

1% → 9000 ÷ 100 = 90

81% → 81 x  90 = 7290

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

90 u = 81% 

90 u = 7290

1 u = 7290 ÷ 90 = 81

Amount that Zeph gave to Min in August
= 100 u
= 100 x 81
= $8100

Amount that Min received less from Zeph from July to August
= 9000 - 8100
= $900

Percentage that the sum given to Min was reduced by from July to August
= ⁹⁰⁰₉₀₀₀ x 100%
= 10%

Answer(s): 10%