Q6 of 202 Page 9

The 6^th and 17^th terms of an A.P. are 19 and 41 respectively, find the 40^th term.

a₆= 19 = a + (n – 1) d

=19 = a + 5d …(i)

A₁₇ = 41 = a + (n – 1) d

= 41 = a + 16d …(ii)

Subtracting (i) from (ii), we get

22 = 11d

d = 2

Now substituting the value of d in (i): 19 = a + 10

= a = 9

A₄₀= a + (40 – 1) 2

= 9 + 78

= 87

How many terms are there in the A.P.?

(i)

(ii)

(iii)

(iv)

The first term of an A.P. is 5, the common difference is 3 and the last term is 80; find the number of terms.

If 9^th term of an A.P. is zero, prove that its 29^th term is double the 19^th term.

If 10 times the 10^th term of an A.P. is equal to 15 times the 15^th term, show that 25^th term of the A.P. is zero.

The 6th and 17th terms of an A.P. are 19 and 41 respectively, find the 40th term.