In October, Ken gave his wife, Xandra, $3000 for household expenditure. Xandra spent 60% of the sum on rental, 30% on food and saved the rest. In November, Ken reduced the sum he gave to Xandra. Xandra 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 November. By what percentage was the sum given to Xandra reduced by?

	Rental	Food	Savings	Total
Before	60%	30%	10%	$3000
Change		- 9%	- ?	- ?
After	60%	21%
Comparing the amounts spent in November	90 u		10 u	100 u

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

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

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

100% → 3000

1% → 3000 ÷ 100 = 30

81% → 81 x  30 = 2430

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

90 u = 81% 

90 u = 2430

1 u = 2430 ÷ 90 = 27

Amount that Ken gave to Xandra in November
= 100 u
= 100 x 27
= $2700

Amount that Xandra received less from Ken from October to November
= 3000 - 2700
= $300

Percentage that the sum given to Xandra was reduced by from October to November
= ³⁰⁰₃₀₀₀ x 100%
= 10%

Answer(s): 10%