Unit 2

4 marks · Normal

A circular swimming pool has a diameter of 16 m. Water is pumped into the pool at a constant rate. The following table shows the depth of water after different times:

(a)

Depth of water over time
Time (minutes)	Depth (m)
10	0.8
20	1.6
30	2.4
40	?

[1 mark]

(b)

Calculate the area of the surface of the pool. Give your answer in standard form.

[2 marks]

(c)

Express the answer from part (b) as an ordinary number.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) 3.2 m

(b) 2.01 \times 10^2 m^2

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Correctly complete the fourth depth value using the pattern (or show calculation of constant increase).

M2 (b) · 1 mark · Use formula A = πr^2 (r = 8). Substitute and work out area.

A1 (b) · 1 mark · Correct area in standard form (2.01×10^2 m^2) to 3 significant figures.

B1 (c) · 1 mark · Correct conversion to ordinary number (201 m^2).

Worked solution

a) Each 10 min, depth increases by 0.8 m. After 40 min: 0.8 × 4 = 3.2 m.

c) In ordinary numbers: 2.01 × 10^2 = 201 m^2.