Question

Find the sum to 10 terms of the A.P., whose kth term is 5k + 1​

Answer 1

Step-by-step explanation:

if n term of a ap in form of an+b where b is constant then the cofficient of n be common difference

here,

Tk = 5k+1 so common difference will be 5

on putting k= 1 we get

T1= 5×1 +1

T1= 6

a= 6 [T1 will be first term of ap i.e a]

now,

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

= 10/2{2×6 +(10-1)5}

= 5(12+9×5)

= 5(12+45)

= 5×57

= 285

hence sum of first 10 term be 285

#666