Mark the correct alternative in the following: If 7th and 13th terms of an A.P. be 34 and 64 respectively, then its 18th term is

Question

Philoid · Accepted Answer

Here,a₇=34 and a₁₃=64

i.e. a+6d=34____(i) and a+12d=64_____(ii)

Subtracting (i) from (ii) we get,

(12-6)d=64-34

∴6d=30

∴ d=5

Substituting d=5 in (i) we get,

a+6(5)=34

∴a+30=34

∴ a=4

Now,18^th term is given by a₁₈=a+17d

=4+17×5

=89