The first term of an AP is 5,the last term is 45 and the sum is 400. find the number of terms and the common difference.
Answers
Answered by
5
a=5
l=45
Sn=400
so,
Sn=n/2(5+45)
400×2=n×50
800/50=n
16=n
so number of terms is 16
an=5+(16-1)d
400-5=(16-1)d
395=(15)d
395/15=d
l=45
Sn=400
so,
Sn=n/2(5+45)
400×2=n×50
800/50=n
16=n
so number of terms is 16
an=5+(16-1)d
400-5=(16-1)d
395=(15)d
395/15=d
Answered by
8
a = 5
l(Last term) = 45
S = 400
★Cross Multiplication :-
n(5 + 45) = 400 × 2
n(50) = 400 × 2
= 8 × 2
= 16
l(Last term) = 45
a + (n - 1)d = 45
5 + (16 - 1)d = 45
5 + 15d = 45
15d = 45 - 5
15d = 40
★Therefore
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