WAEC - Mathematics (2015 - No. 36)
The rate of consumption of petrol by a vehicle varies directly as the square of the distance covered. If 4 litres of petrol is consumed on a distance of 15km. how far would the vehicle go on 9 litres of petrol?
22\(\frac{1}{2}\)km
30km
33\(\frac{1}{2}\)km
45km
Explanation
R \(\alpha\) D2
R = D2K
R = 4 Litres when D = 15cm
thus; 4 = 152k
4 = 225k
k = \(\frac{4}{225}\)
This gives R = \(\frac{4D^2}{225}\)
Where R = 9litres
equation gives
9 = \(\frac{4D^2}{225}\)
9 x 225 = 4d2
D2 = \(\frac{9 \times 225}{4}\)
D = \(\sqrt{9 \times 225}{4}\)
= \(\frac{3 \times 15}{2}\)
= 22\(\frac{1}{2}\)km
R = D2K
R = 4 Litres when D = 15cm
thus; 4 = 152k
4 = 225k
k = \(\frac{4}{225}\)
This gives R = \(\frac{4D^2}{225}\)
Where R = 9litres
equation gives
9 = \(\frac{4D^2}{225}\)
9 x 225 = 4d2
D2 = \(\frac{9 \times 225}{4}\)
D = \(\sqrt{9 \times 225}{4}\)
= \(\frac{3 \times 15}{2}\)
= 22\(\frac{1}{2}\)km
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