In August, Warren gave his wife, Kathy, $6000 for household expenditure. Kathy spent 50% of the sum on rental, 20% on food and saved the rest. In September, Warren reduced the sum he gave to Kathy. Kathy 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 Kathy reduced by?

	Rental	Food	Savings	Total
Before	50%	20%	30%	$6000
Change		- 2%	- ?	- ?
After	50%	18%
Comparing the amounts spent in September	80 u		20 u	100 u

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

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

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

100% → 6000

1% → 6000 ÷ 100 = 60

68% → 68 x  60 = 4080

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

80 u = 68% 

80 u = 4080

1 u = 4080 ÷ 80 = 51

Amount that Warren gave to Kathy in September
= 100 u
= 100 x 51
= $5100

Amount that Kathy received less from Warren from August to September
= 6000 - 5100
= $900

Percentage that the sum given to Kathy was reduced by from August to September
= ⁹⁰⁰₆₀₀₀ x 100%
= 15%

Answer(s): 15%