The theatre had 1645 seats. There were 25% fewer $30-seats than $20-seats. 75% of the $20-seats and some $30-seats were sold. A total of $28350 was collected. How many seats were unsold?

	$30	$20	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 = 1645

1 u = 1645 ÷ 7 = 235

Total number of $20-seat tickets
= 4 u
= 4 x 235
= 940

Number of $20-seat tickets sold
= 75% x 940
= ⁷⁵₁₀₀ x 940
= 705

Amount collected from $20-seat tickets sold
= 705 x 20
= $14100

Amount collected from $30-seat tickets sold
= 28350 - 14100
= $14250

Number of $30-seat tickets sold
= 14250 ÷ 30
= 475

Number of tickets sold
= 705 + 475
= 1180

Number of tickets left unsold
= 1645 - 1180
= 465

Answer(s): 465