Einstein walks on an escalator at a rate of 5steps per second and reaches the other end in 10 sec. while coming back, walking at the same speed he reaches the starting point in 40secs. What is the number of steps on the escalator?
Pick one
A) 22	B) 80	C) 28	D) 17	E) 11
Escalator problems are similar to boats and streams problems. If we assume man's speed as 'a m/s' and escalator speed as 'b m/sec' then while going up man's speed becomes 'a -b' and while coming down 'a + b'.   In this question, Let the speed of escalator be b steps per sec. And length of escalator be L. Einstein's speed = 5 steps/ sec   While going down, L5+x=10L5+x=10 ⇒⇒ L = 50 + 10x   While coming up, L5−x=40L5−x=40 ⇒⇒ L = 200 - 40x   Multiply the first equation by 4, and add to the second, we get L = 80   Answer:80
<result>B</result>
Einstein walks on an escalator at a rate of 5steps per second and reaches the other end in 10 sec. while coming back, walking at the same speed he reaches the starting point in 40secs. What is the number of steps on the escalator?