Question

A took 45 minutes to walk 15 km.if b is 20% faster than a ,how much time he will take to cover the same distance

Answer 1

I think conversion is messing with you. Here is another method.

Speed is in Km per M
or Speed is Km/m i.e Km divided by Minute
Speed=D/T
Let A's speed be 15/45

B is 20% faster
15/45 + 15/45*20/100 = 15/45 + 3/45 = 18/45

Now distance is same so what should be in place of 45(m) if km is 15
[This means value of 18/45 should remain same]
Let x be time taken by B
15/x= 18/45
15*45/18=x
x=75/2
x=37.5m
37 and 30 sec

Conventional method

Speed of A=15/45 =1/3 Km/m

Speed of B= 1/3 + 1/3*20/100 =1/3 + 20/300
=120/300= 2/5

Distance is same. Time taken
Time= 15/2/5
Time=15*5/2
Time=75/2
Time=37.5