What is the sum of first 40 terms of 1 3 4 5 7 7 10 9 hellip ........

Quantitative Aptitude (CGL) Arithmetic progression

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What is the sum of first 40 terms of 1 + 3 + 4 + 5 + 7 + 7 + 10 + 9 + ….?

1010

1115

1030

1031

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Explanation:

S1=1+4+7+10+…( AP with A1=1,D1=3)
S2=3+5+7+9+...(AP with A2=3,D2=2)
Sum of 40 terms of the original series = Sum of 20 terms of S1+ Sum of 20 terms of S2
S=N[2A1+(N−1)D1]/2+N[2A2+(N−1)D2]/2
?S=[20∗((2∗1)+(19∗3))]+[20∗((2∗3)+(19∗2)]/2
?S=10∗[59+44]=1030