Question

in an Ap, if comman differance is 2, sum to n terms is 49 7th term is 13 then n equql

Answer 1

Answer:

Step-by-step explanation:

a+(7-1)d=13

2+6d=13

d=11/6

n/2(2*2+(n-1)11/6)=49

Using this u can solve

Answer 2

Answer:

n = 7

Step-by-step explanation:

Here Common Difference (d) = 2

Let first term be a

7th term = 13

∴ a + 6d = 13    [∵ nth term = a + (n - 1)d]

Putting value of d

a + 12 = 13

a = 1

Now

Sum of n terms (Sn) = 49

We know that sum of n terms = n/2[2a + (n - 1 )d]

∴ n/2[2a + ( n - 1)d] = 49

Putting value of a and d

n/2[2 + ( n - 1 ) 2] = 49

n [ 2 + 2n - 2] = 49 × 2

n [ 2n ] = 49 × 2

n² = 49

n = 7 or -7  (neglecting n = -7 because number of terms can not be negative)

Hence n = 7