Mary bought 4 portable air-conditioners and 8 hand blenders. Each portable air-conditioner costs $408 more than each hand blender. She spent 10% of her money on the hand blenders.

1. How much did each portable air-conditioner cost? 
2. How much did she spend altogether?

	Portable air-conditioners	Hand blenders	Total
Number	4	8
Value	1 u + $408	1 u
Total value	4 u + $1632	8 u
Comparing amounts spent on portable air-conditioners and hand blenders	90%	10%	100%

(a)
Amount that Mary spent on the portable air-conditioners
= 4(1 u + 408)
= 4 u + 1632 

Amount that Mary spent on the hand blenders
= 8 x 1 u
= 8 u

Amount that Mary spent on the portable air-conditioners in percent
= 100% - 10%
= 90%

10% → 8 u

90% → 9 x 8 u = 72 u

72 u = 4 u + 1632
72 u - 4 u = 1632
68 u = 1632

1 u = 1632 ÷ 68 = 24

Cost of each portable air-conditioner 
= 24 + 408
= $432

(b)
100% → 8 u + 72 u = 80 u

Amount that Mary spent altogether
= 80 u
= 80 x 24
= $1920

Answer(s): (a) $432; (b) $1920