Carl had a total of 150 notes. The notes are $2 notes and $10 notes. After he spent 80% of the $2 notes and 75% of the $10 notes on one lamp, he was left with 5 times as many $10 notes as $2 notes. How much did the lamp cost?

	$2	$10
Before	5x1 = 5 u	4x5 = 20 u
Change	- 4x1 = - 4 u	- 3x5 = - 15 u
After	1x1 = 1 u	1x5 = 5 u
Comparing $2 and $10 in the end	1x1  = 1 u	5x1 = 5 u

80% of $2 notes = ⁸⁰
₁₀₀ of $2 notes = ⁴₅ of $2 notes
75% of $10 notes = ⁷⁵₁₀₀ of $10 notes = ³₄ of $10 notes

The number of $2 notes in the end is repeated.  Make the number of $2 notes the same.  LCM of 1 and 5 is 5.

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

Number of notes at first
= 5 u + 20 u
= 25 u

25 u = 150

1 u = 150 ÷ 25 = 6

	$2	$10
Number	4 u	15 u
Value	2	10
Total value	8 u	150 u

Value of $2 spent
= 4 u x 2
= 8 u

Value of $10 spent
= 15 u x 10
= 150 u

Price of the lamp
= 8 u + 150 u
= 158 u
= 158 x 6
= $948

Answer(s): $948