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Question
Find the sum of the following APs.
0.6, 1.7, 2.8, …….., to 100 terms.
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Solution
0.6, 1.7, 2.8, …, to 100 terms
For this A.P.,
a = 0.6
d = a2 − a1
= 1.7 − 0.6
d = 1.1
n = 100
We know that
Sn = `n/2[2a+(n-1)d]`
S100 = `100/2[2(0.6)+(100 - 1)1.1]`
= 50[1.2 + (99) × (1.1)]
= 50[1.2 + 108.9]
= 50[110.1]
= 5505
Thus, the required sum of first 100 terms is 5505.
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