Complete the following activity to find the sum of all natural numbers between 1 and81 divisible by 8.
The number between 1 and 81 divisible by 8 are 8,16,24,… , 80.
Here, `a= t_(1) = 8, d= 8, t_(n) = 80, n = ? , S_(n) = ?`
`t_(n) square ` ...(Formula)
` :. 80 = 8 + square ` ....(Substituting the values )
`:. 80 = square `
`:. n = 10`
Now, we find `S_(10)`.
`S_(n ) = ( n )/(2) square ` ...(Formula )
`:. S_(10) = (10)/(2) xx square ` ....(Substituting the values )
`:. S_(10) = square `
