Two people leave a junction simultaneously, one travelling North and the other travelling West. One of them runs at a speed of 2 km/h more than the other. If after two hours from start, they are 20 kms apart, the speed of the faster person is:
Explanation:
Let the speed of the faster person be x kmph, then speed of the slower person be (x - 2) km/h.
Distance travelled by them in 2 hours will be, 2x and 2(x - 2) kms.
∴ (2x)2 + (2(x - 2))2 = 202
⇒ 8x2 – 16x + 16 = 400
⇒ 8x2 – 16x - 384 = 0
⇒ x2 – 2x - 48 = 0
⇒ x = 8 or -6. (-6 will be rejected)
∴ Speed of the faster person is 8 kmph.
Hence, option (b).
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