Question

The 7th term of an AP is 20 and 13th term is 32.find 40th term of the Ap

Answer 1

Answer:

86

Step-by-step explanation:

a+6d=20

a+12d=32

By elimination method

6d=12

d=2

a=20-6(2)

a=8

a40=a+39d

=8+39(2)

=8+78

=86

Answer 2

EXPLANATION.

• GIVEN

7th term of an Ap = 20

13th term of an Ap = 32

Find 40th term of an Ap.

Nth term of an Ap

=> An = a + ( n - 1 )d

=> Case = 1

=> 7th term of Ap = 20

=> a + 6d = 20 ......(1)

Case = 2

=> 13th term of an Ap = 32

=> a + 12d = 32 .......(2)

From equation (1) and (2) we get,

=> -6d = -12

=> d = 2

put the value of d = 2 in equation (1)

we get,

=> a + 6(2) = 20

=> a + 12 = 20

=> a = 8

40th term of an Ap.

=> a + 39d

=> 8 + 39(2)

=> 8 + 78

=> 86

Therefore,

40th term of an Ap = 86