Question

200 logs are stacked in the following manner 20 logs in the bottom roll 19 in the next row 18 in the road next to it and so on in how many rows are 200 logs please and how many locks are in the top row?

Answer 1

Hope it helps................ See in attachment

Answer 2

let a=20 ,d=-1 and n=? Sn=200

Sn=n/2{2a+(n-1)d}

200= n/2{2(20)+(n-1)(-1)}

400=n{40-n+1}

400=41n-n^2

n^2-41n+400=0

On solving the quadratic equation,we get:

n=16,25

now,

Tn=a+(n-1)d

=20+15×-1

=20-15

=5