In an a.p 2+7+12...find the sum of first 20 terms
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Hey mate this is your answer
difference = 5
a = 2
n = 20
An = a + ( n - 1 ) × d
an = 2 + ( 20 - 1 ) × 5
an = 2 + ( 19 ) × 5
an = 2 + 95
an = 97
sn = n / 2 × ( a + an )
sn = 20 / 2 × ( 2 + 97 )
sn = 10 × ( 99 )
sn = 990
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