The figure shows the amount of water in two rectangular tanks, M and N, at first. Pierre poured ¹₄ of the water from M into N to fill it to the top, without overflowing.

1. How much water was there in Tank M at first?
2. Pierre then poured all the water from Tank N into Tank M. 5220 cm³ of water overflowed from Tank M. What was the height of Tank M?

(a)
Volume of water to fill Tank N
= 18 x 15 x 16
= 4320 cm<sup>3

1</sup>₄ of volume of water in Tank M at first = 4320 cm^3  
4₄ of volume of water in Tank M at first = 4 x 4320 = 17280 cm³

Volume of water in Tank M at first = 17280 cm³

Volume of water in Tank N at first
= 18 x 15 x 18
= 4860 cm³

Total volume of water in Tank M and Tank N 
= 17280 + 4860
= 22140 cm³

Final volume of water in Tank M after 5220 cm³ of water overflowed
= 22140 - 5220
= 16920 cm³

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

Height of Tank M
= 16920 ÷ 360 
= 47 cm

Answer(s): (a) 17280 cm² ; (b) 47 cm