Find the number of terms of an A.P. which has its first term 2 common difference 2 and the sum 420
Answer:40
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Step-by-step explanation:
Solution:
a=7 l=49 Sn=420
Sn= 2 n
[a+l]
So 420×2=n[7+49]
n=15
l=a+(n−1)d
⇒ 49=7+14 d
⇒ 7=1+2 d ⇒ 2d=6
⇒ d=3
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