The drama centre had 1912 seats. There were 40% fewer $30-seats than $20-seats. 80% of the $20-seats and some $30-seats were sold. A total of $30280 was collected. How many seats were unsold?

	$30	$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 = 1912

1 u = 1912 ÷ 8 = 239

Total number of $20-seat tickets
= 5 u
= 5 x 239
= 1195

Number of $20-seat tickets sold
= 80% x 1195
= ⁸⁰₁₀₀ x 1195
= 956

Amount collected from $20-seat tickets sold
= 956 x 20
= $19120

Amount collected from $30-seat tickets sold
= 30280 - 19120
= $11160

Number of $30-seat tickets sold
= 11160 ÷ 30
= 372

Number of tickets sold
= 956 + 372
= 1328

Number of tickets left unsold
= 1912 - 1328
= 584

Answer(s): 584