Ratio of speeds of A and B = 3 : 4
∴ Ratio of time taken = 4 : 3
Let time taken by A and B be 4k and 3k, respectively.
Then, according to the question,
4k - 3k = 20
⇒ k = 20
Hence, time taken by A = 4 x 20 = 80 min
And time taken by B = 3 x 20 = 60 min
