An absent minded scientist walks on an escalator at a rate of 4 steps per second and reaches the other end in 15 seconds. While coming back, walking at the same speed he reaches the starting point in 45 seconds. What is the number of steps on the escalator?
A. ক 60
B. খ 90
C. গ 150
D. ঘ 120
সঠিক উত্তরঃ
D.
ঘ 120
Explanation:
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