The theatre had 1575 seats. There were 25% fewer $35-seats than $10-seats. 60% of the $10-seats and some $35-seats were sold. A total of $18560 was collected. How many seats were unsold?

	$35	$10	Total
Number	3 u	4 u	7 u

100% - 25% = 75%
⁷⁵₁₀₀ = ³₄

Total number of seats
= 3 u + 4 u
= 7 u

7 u = 1575

1 u = 1575 ÷ 7 = 225

Total number of $10-seat tickets
= 4 u
= 4 x 225
= 900

Number of $10-seat tickets sold
= 60% x 900
= ⁶⁰₁₀₀ x 900
= 540

Amount collected from $10-seat tickets sold
= 540 x 10
= $5400

Amount collected from $35-seat tickets sold
= 18560 - 5400
= $13160

Number of $35-seat tickets sold
= 13160 ÷ 35
= 376

Number of tickets sold
= 540 + 376
= 916

Number of tickets left unsold
= 1575 - 916
= 659

Answer(s): 659