The theatre had 2556 seats. There were 20% fewer $40-seats than $20-seats. 50% of the $20-seats and some $40-seats were sold. A total of $31120 was collected. How many seats were unsold?

	$40	$20	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 = 2556

1 u = 2556 ÷ 9 = 284

Total number of $20-seat tickets
= 5 u
= 5 x 284
= 1420

Number of $20-seat tickets sold
= 50% x 1420
= ⁵⁰₁₀₀ x 1420
= 710

Amount collected from $20-seat tickets sold
= 710 x 20
= $14200

Amount collected from $40-seat tickets sold
= 31120 - 14200
= $16920

Number of $40-seat tickets sold
= 16920 ÷ 40
= 423

Number of tickets sold
= 710 + 423
= 1133

Number of tickets left unsold
= 2556 - 1133
= 1423

Answer(s): 1423