The drama centre had 2025 seats. There were 20% fewer $30-seats than $15-seats. 80% of the $15-seats and some $30-seats were sold. A total of $24000 was collected. How many seats were unsold?

	$30	$15	Total
Number	4 u	5 u	9 u

100% - 20% = 80%
⁸⁰₁₀₀ = ⁴₅

Total number of seats
= 4 u + 5 u
= 9 u

9 u = 2025

1 u = 2025 ÷ 9 = 225

Total number of $15-seat tickets
= 5 u
= 5 x 225
= 1125

Number of $15-seat tickets sold
= 80% x 1125
= ⁸⁰₁₀₀ x 1125
= 900

Amount collected from $15-seat tickets sold
= 900 x 15
= $13500

Amount collected from $30-seat tickets sold
= 24000 - 13500
= $10500

Number of $30-seat tickets sold
= 10500 ÷ 30
= 350

Number of tickets sold
= 900 + 350
= 1250

Number of tickets left unsold
= 2025 - 1250
= 775

Answer(s): 775