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

1. How much water was there in Tank B at first?
2. Sam then poured all the water from Tank C into Tank B. 6540 cm³ of water overflowed from Tank B. What was the height of Tank B?

(a)
Volume of water to fill Tank C
= 15 x 13 x 15
= 2925 cm<sup>3

1</sup>₅ of volume of water in Tank B at first = 2925 cm^3  
5₅ of volume of water in Tank B at first = 5 x 2925 = 14625 cm³

Volume of water in Tank B at first = 14625 cm³

Volume of water in Tank C at first
= 15 x 13 x 17
= 3315 cm³

Total volume of water in Tank B and Tank C 
= 14625 + 3315
= 17940 cm³

Final volume of water in Tank B after 6540 cm³ of water overflowed
= 17940 - 6540
= 11400 cm³

Base area of Tank B
= 20 x 15
= 300 cm²

Height of Tank B
= 11400 ÷ 300 
= 38 cm

Answer(s): (a) 14625 cm² ; (b) 38 cm