Choose the correct choice in the following and justify : (i) 30th term of the AP: 10,7,4,..., is (A) 97 (B) 77 (C) −77 (D) 87 (ii) 11th term of the AP: −3,−12,2,...., is (A) 28 (B) 22 (C) 38 (D) −4812
Open in App
Solution
(i) Given that A.P. 10,7,4,… First term, a=10 Common difference, d=a2=a1=7−10=−3
We know that an=a+(n−1)d
a30=10+(30−1)(−3)
=10+(29)(−3)
=10−87
=−77 Hence, the correct answer is option C.
(ii) A.P. is −3,−12,2,......
First term a=−3 Common difference, d=a2−a1=−12−(−3)=52