Find the sum of first 20 terms of ap 3,7 11,15....using formula
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42
≡QUESTION≡
Find the sum of first 20 terms of an AP 3,7 11,15...
║⊕ANSWER⊕║
The AP is 3 , 7, 11, 15....
a = 3
d = 4
Formula used = Sₙ = n/2 [2a + (n-1) d]
S₂₀ = 20 / 2 [ 2*3 + 19*4]
= 10 [ 6 + 76]
= 10 * 82
= 820
Answered by
16
Answer:
a=3,d=7-3=4, n=20
Step-by-step explanation:
an=a+(n-1)×d
=3+(20-1)×4
=3+19×4
=79
so, 79 is the 20th term of ap..
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