Question

A devotee climbs a mountain 17 steps in the first minutes 15 steps in the second minute and 13 steps in the third minute and so on if he reached the last step in 9 minutes Find the number of steps he climbed​

Answer 1

Answer: Sn = 81

Step-by-step explanation:

n=9

a=17

d=-2

1, 2, 3....9=time consumed

17,15,13....1=no. of steps

Sn=n/2 [2a+(n-1)d]

Sn=9/2 [2(17)+(8)-2]

Sn=9/2 [34-16]

Sn=9/2 [18]

Sn= 9[9]

Sn= 81