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

1. How much water was there in Tank C at first?
2. John then poured all the water from Tank D into Tank C. 3696 cm³ of water overflowed from Tank C. What was the height of Tank C?

(a)
Volume of water to fill Tank D
= 16 x 13 x 14
= 2912 cm<sup>3

1</sup>₅ of volume of water in Tank C at first = 2912 cm^3  
5₅ of volume of water in Tank C at first = 5 x 2912 = 14560 cm³

Volume of water in Tank C at first = 14560 cm³

Volume of water in Tank D at first
= 16 x 13 x 17
= 3536 cm³

Total volume of water in Tank C and Tank D 
= 14560 + 3536
= 18096 cm³

Final volume of water in Tank C after 3696 cm³ of water overflowed
= 18096 - 3696
= 14400 cm³

Base area of Tank C
= 20 x 16
= 320 cm²

Height of Tank C
= 14400 ÷ 320 
= 45 cm

Answer(s): (a) 14560 cm² ; (b) 45 cm