One of the basic question from Arithmetic Progression Chapter of ML Aggarwal and we have to asked to determine Find the sum of the following APs: (i) 2,7,12,…, to 10 terms.(iv) 1/15, 1/21, 1/10 ,…., to 11 terms.
Rajan@2021Guru
Find the sum of the following APs: (i) 2,7,12,…, to 10 terms.(iv) 1/15, 1/21, 1/10 ,…., to 11 terms.
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(i) 2,7,12...... to 10th term
Here a=2,n=10
And d=7−2=5
Sn=2n[2a+(n−1)d]
S10=210[2(2)+(10−1)5]=5(4+9×5)=245
(ii)151,121,101....... to 11th term
a=151, n=11
d=121−151=605−4=601
S11=211[2(151+(11−1)601)]
= 211(152+6010)
= 211×309=2033