On the world environment day tree plantation programme was arranged on a land which is triangular in shape. Trees are planted such that in the first row there is one tree, in the second row there are two tree, in the third row three trees and so on. Find the total number of trees in 25 rows.

Answer

Total number of trees are 325.

Explanation

The number of trees increases by 1 in consecutive rows. `therefored=1`
There is one tree in the first row. `thereforea=1`
This is an A.P. There are 25 rows. `thereforen=25`.
So, we have to find the total number of trees in 25 rows. It means, we have to find `S_(25)`.
`S_(n)=(n)/(2)[2a+(n-1)d]` ...(Formula)
`thereforeS_(25)=(25)/(2)[2xx1+(25-1)xx1]` ...(Substituting the values)
`=(25)/(2)[2+24xx1]`
`=(25)/(2)[2+24]`
`=(25)/(2)xx26=25xx13`
`thereforeS_(25)=325`