The drama centre had 1576 seats. There were 40% fewer $40-seats than $20-seats. 80% of the $20-seats and some $40-seats were sold. A total of $30640 was collected. How many seats were unsold?

	$40	$20	Total
Number	3 u	5 u	8 u

100% - 40% = 60%
⁶⁰₁₀₀ = ³₅

Total number of seats
= 3 u + 5 u
= 8 u

8 u = 1576

1 u = 1576 ÷ 8 = 197

Total number of $20-seat tickets
= 5 u
= 5 x 197
= 985

Number of $20-seat tickets sold
= 80% x 985
= ⁸⁰₁₀₀ x 985
= 788

Amount collected from $20-seat tickets sold
= 788 x 20
= $15760

Amount collected from $40-seat tickets sold
= 30640 - 15760
= $14880

Number of $40-seat tickets sold
= 14880 ÷ 40
= 372

Number of tickets sold
= 788 + 372
= 1160

Number of tickets left unsold
= 1576 - 1160
= 416

Answer(s): 416