The drama centre had 1440 seats. There were 20% fewer $25-seats than $10-seats. 80% of the $10-seats and some $25-seats were sold. A total of $17500 was collected. How many seats were unsold?

	$25	$10	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 = 1440

1 u = 1440 ÷ 9 = 160

Total number of $10-seat tickets
= 5 u
= 5 x 160
= 800

Number of $10-seat tickets sold
= 80% x 800
= ⁸⁰₁₀₀ x 800
= 640

Amount collected from $10-seat tickets sold
= 640 x 10
= $6400

Amount collected from $25-seat tickets sold
= 17500 - 6400
= $11100

Number of $25-seat tickets sold
= 11100 ÷ 25
= 444

Number of tickets sold
= 640 + 444
= 1084

Number of tickets left unsold
= 1440 - 1084
= 356

Answer(s): 356