In September, Flynn gave his wife, Opal, $8000 for household expenditure. Opal spent 50% of the sum on rental, 30% on food and saved the rest. In October, Flynn reduced the sum he gave to Opal. Opal spent the same amount on rental and reduced the amount she spent on food by 30%. She saved the remaining 20% of the sum given to her in October. By what percentage was the sum given to Opal reduced by?

	Rental	Food	Savings	Total
Before	50%	30%	20%	$8000
Change		- 9%	- ?	- ?
After	50%	21%
Comparing the amounts spent in October	80 u		20 u	100 u

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

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

Total amount that Flynn spent on rental and food in percent
= 50% + 21%
= 71%

100% → 8000

1% → 8000 ÷ 100 = 80

71% → 71 x  80 = 5680

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

80 u = 71% 

80 u = 5680

1 u = 5680 ÷ 80 = 71

Amount that Flynn gave to Opal in October
= 100 u
= 100 x 71
= $7100

Amount that Opal received less from Flynn from September to October
= 8000 - 7100
= $900

Percentage that the sum given to Opal was reduced by from September to October
= ⁹⁰⁰₈₀₀₀ x 100%
= 11.25%

Answer(s): 11.25%