Car A travels x km for every litre of petrol, while car B travels (x + 5) km for every litre of petrol. (i) Write down the number of litres of petrol used by car A and car B in covering a distance of 400 km. (ii) If car A use 4 litre of petrol more than car B in covering the 400 km, write down and equation in x and solve it to determine the number of litre of petrol used by car B for the journey.

Smita Gochhayat · 18th Feb 2019 .

Car A travels x km for every litre of petrol, while car B travels (x + 5) km for every litre of petrol.

(i) Write down the number of litres of petrol used by car A and car B in covering a distance of 400 km.

(ii) If car A use 4 litre of petrol more than car B in covering the 400 km, write down and equation in x and solve it to determine the number of litre of petrol used by car B for the journey.

Subhadra Jena · 18th Feb 2019 .

Given Distance = 400 km

Car A travels x km/litre

Car B travels (x + 5) km/ litre.

(i) No, of litre used by car

A = Distance/Speed of car A

= 400/x litre

No. of litre used by car B = Distance/Speed of car B

= 400/x + 5 litre

(ii) Car A uses 4 litre more than car B

∴ 400/x – 400/x + 5 = 4

400(x + 5) – 400x = 4x(x + 5)

400x + 2000 – 400x = 4x2 +20x

4x2 + 20x – 2000 = 0

4(x2 + 5x – 500) = 0

x2 + 25x – 20x – 500 = 0

x(x + 25) – 20(x + 25) = 0

(x + 25)(x – 20) = 0

∴ x = 20 – 25 (inadmissible)

No. of litre of petrol used by car B

= 400/20 + 5 = 800/25 = 16

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