The figure shows the amount of water in two rectangular tanks, X and Y, at first. Eric poured ¹₅ of the water from X into Y to fill it to the top, without overflowing.

1. How much water was there in Tank X at first?
2. Eric then poured all the water from Tank Y into Tank X. 11520 cm³ of water overflowed from Tank X. What was the height of Tank X?

(a)
Volume of water to fill Tank Y
= 18 x 15 x 15
= 4050 cm<sup>3

1</sup>₅ of volume of water in Tank X at first = 4050 cm^3  
5₅ of volume of water in Tank X at first = 5 x 4050 = 20250 cm³

Volume of water in Tank X at first = 20250 cm³

Volume of water in Tank Y at first
= 18 x 15 x 17
= 4590 cm³

Total volume of water in Tank X and Tank Y 
= 20250 + 4590
= 24840 cm³

Final volume of water in Tank X after 11520 cm³ of water overflowed
= 24840 - 11520
= 13320 cm³

Base area of Tank X
= 20 x 18
= 360 cm²

Height of Tank X
= 13320 ÷ 360 
= 37 cm

Answer(s): (a) 20250 cm² ; (b) 37 cm