How i solve the problem of exercise 5.3 question no.5 .Please help me sir to solve this question in a easy way . 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.
AnilSinghBoraGuru
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. Q.5
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Given that,
first term, a = 5
last term, l = 45
Sum of the AP, Sn = 400
As we know, the sum of AP formula is;
Sn = n/2 (a+l)
400 = n/2(5+45)
400 = n/2(50)
Number of terms, n =16
As we know, the last term of AP series can be written as;
l = a+(n −1)d
45 = 5 +(16 −1)d
40 = 15d
Common difference, d = 40/15 = 8/3