Question

Reena climbs up 5 stairs every second and then climb down 2 stairs over the next second how many seconds will take to climb 60 stairs

Answer 1

Answer:

She will climb 60 stairs on 39 seconds.

Step-by-step explanation:

Reena climbs up 5 stairs every second

She climb down 2 stairs over the next second

The net climb for Reena is 3 stairs per 2 seconds.

Total she has to climb is 60 stairs

So she should take (60/3) *2=40 seconds.

Since in the last second she will not fall, she will reach a second before, that is by 39th second.

Answer 2

Answer:

⇒ Time taken by Reena to climb 60 stairs = 39 seconds

Step-by-step explanation:

Given that : Reena climbs up 5 stairs every second and then climbs down 2 stairs over the next second

⇒ Reena climbs (5 - 2) stairs in total after (1 + 1) seconds

⇒ Reena climbs 3 stairs in total after 2 seconds

⇒ Rate at which Reena climbs = 1 stair per 2/3 seconds

$\text{So, Time taken by Reena to climb 60 stairs = }\frac{2}{3}\times 60=40\text{ seconds}$

But, when she climbs the last 5 stairs then she will reach the 60 stairs already so she will not have to climb down the next second so, as a result saving one second of climbing.

⇒ Time taken by Reena to climb 60 stairs = 40 - 1 = 39 seconds