PSLE
Linda spent $810 in November. This amount was a 10% decrease from what she spent in October. The amount she spent in December was a 10% increase from what she spent in November.

1. What was the total amount that Linda spent from October to December?
2. What was the percentage decrease in the amount Linda spent in December compared to October?

	Spending
October	100%
Change	- 10%
November	90%	100 u
Change		+ 10 u
December		110 u

(a)
Spending in October = 100%
Spending in November = 100% - 10% = 90%

90% = 810

1% = 810 ÷ 90 = 9

Spending in October
= 100% 
= 100 x 9
= $900

Spending in November = 100 u
Spending in December = 100 u + 10 u = 110 u 

100 u = 810

1 u = 810 ÷ 100 = 8.1

Spending in December
= 110 u
= 110 x 8.1
= $891

Total spending from October to December
= 900 + 810 + 891
= $2601

(b)
Decrease in spending in December compared to October
= 900 - 891 
= $9

Percentage decrease
= ^{Decrease in spending}_{Spending in October} x 100%
= ⁹₉₀₀ x 100%
= 1%

Answer(s): (a) $2601; (b) 1%