Find the sum of 1st 12 terms of the AP 15,18,21,24.....
Answers
Answered by
0
Step-by-step explanation:
n = 12
an = a + (n − 1) × d
a = 1st number = 15
d = difference = 18 - 15 = 3
a12 = 15 + (12-1) × 3
= 15 + 11×3
= 15 +33 = 48
Answered by
0
Step-by-step explanation:
sn = n/2 (2a+(n-1)d )
here,
n=12
a=15
d=18-15=3
s12 = 12/2 (2(15)+(12-1)3)
s12 = 6(30+11(3))
s12 = 6(30+33)
s12 = 6(63)
s12 = 378
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