Carl had a total of 105 notes. The notes are $10 notes and $2 notes. After he spent 90% of the $10 notes and 80% 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	10x1 = 10 u	5x5 = 25 u
Change	- 9x1 = - 9 u	- 4x5 = - 20 u
After	1x1 = 1 u	1x5 = 5 u
Comparing $10 and $2 in the end	1x1  = 1 u	5x1 = 5 u

90% of $10 notes = ⁹⁰
₁₀₀ of $10 notes = ⁹₁₀ of $10 notes
80% of $2 notes = ⁸⁰₁₀₀ of $2 notes = ⁴₅ of $2 notes

The number of $10 notes in the end is repeated.  Make the number of $10 notes the same.  LCM of 1 and 5 is 5.

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

Number of notes at first
= 10 u + 25 u
= 35 u

35 u = 105

1 u = 105 ÷ 35 = 3

	$10	$2
Number	9 u	20 u
Value	10	2
Total value	90 u	40 u

Value of $10 spent
= 9 u x 10
= 90 u

Value of $2 spent
= 20 u x 2
= 40 u

Price of the toaster oven
= 90 u + 40 u
= 130 u
= 130 x 3
= $390

Answer(s): $390