Travelling at 3/4 of the normal speed, a person reaches his workplace 15 minutes late. How many minutes does he take usually to reach the workplace?

Correct option is D

Given:
Travelling at 3/4 of the normal speed, a person reaches his workplace 15 minutes late
Formula Used:
Distance = Speed × Time
Solution:
Let the normal speed of person be x m/s, time taken = y
Thus, distance = xy
As per the question

Alternate Method:
Let the normal speed be 4 km/hr
Travelling speed = 4 × (3/4) = 3 km/hr
Ratio of normal speed to travelling speed = 4x : 3x
As we know,
Time is inversely proportional to time.
Ratio of normal time to travelling time = 3x : 4x
4x – 3x = 15
⇒ x = 15
∴ Normal time = 3x = 3 × 15 = 45 min