Question

If 7th and 13th terms of an A.P. be 34 and 64 respectively, then its 18th term is (a) 87 (b) 88 (c) 89 (d) 90

Answer 1

Correct Answer - 89
a+6d =34 ` " " (i) " " and " " a+12d =64`
On solving (i) and (ii), we get a=4 and d=5
` T_(180 =a +17d = ( 4+17 xx5) =89`