Walking 3/5 of his normal speed, Sami is 20 minutes late in reaching his coaching. The usual time taken by him to cover the distance between his home and coaching ?

Question: Walking 3/5 of his normal speed, Sami is 20 minutes late in reaching his coaching. The usual time taken by him to cover the distance between his home and coaching ?

Solution:
Let,
Distance y meter and speed x meter/min.
usual time taken y/x min

According to the question,
(y/3x/5) - (y/x) = 20
⇒ (y/x) {(5/3) - 1} = 20
⇒ (y/x) (2/3) = 20
∴ (y/x) = 30

∴ The usual time taken by Sami to reach his coaching = 30 minutes