Question

Q.25 If a man walks 1 km./hr. faster
than his usual speed he covers a
distance of 4 km in 20 minutes less
time then his usual speed will
be
4 km/hr
5 km/hr
3 km/hr
2 km/hr​

Answer 1

Answer:

5 km per hour

Answer 2

Answer:

c) 3 km/hr

Solution:

Let the usual speed of man be x km/h.

Time taken to cover 3 km at usual speed = 3/x hr

Actual speed of man = x + 1 km/h

Time taken to cover 3 km at actual speed = 3/(x + 1) hr

According to the Question,

⇒ 3/x - 3/(x + 1) = 15/60

⇒ 3/x - 3/(x + 1) = 1/4

⇒ 1/x - /1(x + 1) = 1/12

⇒ (x + 1) - 1/x(x + 1) = 1/12

⇒ 1/(x² + x) = 1/12

⇒ x² + x - 12 = 0

⇒ x² + 4x - 3x - 12 = 0

⇒ x(x + 4) - 3(x + 4) = 0

⇒ (x + 4) (x - 3) = 0

⇒ x + 4 = 0 or x - 3 = 0

⇒ x = - 4, 3 (As x can't be negative)

⇒ x = 3

Hence, the usual speed of men is 3 km/h.

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