Carl had a total of 90 notes. The notes are $10 notes and $2 notes. After he spent 90% of the $10 notes and 60% of the $2 notes on one toaster oven, he was left with 5 times as many $2 notes as $10 notes. How much did the toaster oven cost?

	$10	$2
Before	10x2 = 20 u	5x5 = 25 u
Change	- 9x2 = - 18 u	- 3x5 = - 15 u
After	1x2 = 2 u	2x5 = 10 u
Comparing $10 and $2 in the end	1x2  = 2 u	5x2 = 10 u

90% of $10 notes = ⁹⁰
₁₀₀ of $10 notes = ⁹₁₀ of $10 notes
60% of $2 notes = ⁶⁰₁₀₀ of $2 notes = ³₅ of $2 notes

The number of $10 notes in the end is repeated.  Make the number of $10 notes the same.  LCM of 2 and 5 is 10.

The number of $2 notes in the end is repeated. Make the number of $2 notes the same. LCM of 1 and 2 is 2.

Number of notes at first
= 20 u + 25 u
= 45 u

45 u = 90

1 u = 90 ÷ 45 = 2

	$10	$2
Number	18 u	15 u
Value	10	2
Total value	180 u	30 u

Value of $10 spent
= 18 u x 10
= 180 u

Value of $2 spent
= 15 u x 2
= 30 u

Price of the toaster oven
= 180 u + 30 u
= 210 u
= 210 x 2
= $420

Answer(s): $420