Foundation June 2017 Paper 2 Q21

AQACurrent spec6 marksPrisms

21 Eva thinks she can save water by having a shower instead of a bath.

Eva’s shower

uses 10.8 litres per minute
lasts for 8 minutes.

Eva assumes that the water in her bath is in the shape of this cuboid.

1000 cm\(^3\) = 1 litre

(a) Using Eva’s assumption, work out how many litres of water she saves by having a shower instead of a bath. [5 marks]

(b) \(A\) shows the water level before Eva gets into the bath.

\(B\) shows the cuboid in the empty bath.

Not drawn accurately

What does this tell you about the amount of water saved? [1 mark]

Mark scheme (a)

Answer	Mark	Comments
Alternative method 1
\(10.8 \times 8\) or 86.4	M1
\(50 \times 110 \times 35\) or 192 500	M1	Must use correct volume formula
their 192 500 \(\div\) 1000 or 192.5	M1dep	dep on 2nd M1
their 192.5 \(-\) their 86.4	M1dep	dep on M1M1M1
106.1 or 106	A1
Alternative method 2
\(10.8 \times 8 \times 1000\) or 86 400	M1	oe
\(50 \times 110 \times 35\) or 192 500	M1	Must use correct volume formula
their 192 500 \(-\) their 86 400 or 106 100	M1dep	dep on M1M1
their 106 100 \(\div\) 1000	M1dep	dep on M1M1M1
106.1 or 106	A1

Mark scheme (b)

Answer	Mark	Comments
A comment that the answer to part (a) was too low or that the amount saved would be greater	B1

It was more	B1
More water saved	B1
She underestimated it	B1
She underestimated the water saved	B1
She’s saving more water because she’s using more water than the cuboid	B1
Greater than 106.1 litres (may need to check value in part (a) if they quote a different value)	B1
More than Eva’s assumption	B1
Eva’s assumption was not accurate therefore the prediction was wrong	B0
She underestimated the water	B0
Less water used	B0
It was inaccurate	B0
A uses more water than B (only talking about the diagram)	B0
B saves more than A (only talking about the diagram)	B0
Saves a lot of water	B0
More water used	B0
Cuboid smaller than bath	B0
Used more water in the bath than she thought	B0