Q4 of 23 Page 1

Attempt of the following question:

The 11th term and the 21st term of an A.P. are 16 and 29 respectively, then find:
a) The first term and common difference.
b) The 34th term.
c) ‘n’ such that tn = 55.

We know that t11 = 16 and t29 = 29


Also, ⇒


∴16 = a + (11-1)d


∴16 = a + 10d---let say eqn 1


and


∴29 = a + (21-1)d


∴29 = a + 20d---let say eqn 2


eqn2-eqn1


(29-16) = a-a + (20-10)d



Substitute in eqn 1
16 = a + 10 × 1.3


∴a = 3


The 34th term will be



N such that


t_n = a + (n-1)d


55 = 3 + (n-1) × 1.3





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