Question

the first term of AP is 5 the last term is 2
45 and the sum is 400 find the number of terms and common difference

Answer 1

Heya !!

Here is your answer :-

Given : a= 5, l = 245
Sn = 400

Sn= n/2(a+l)

=>400 = n/2 (5+245)
=> 400 = n/2 (250)
=> 400 = 125n
=> 400/125 = n
=> 3.2 = n

Now, an = a + (n-1)d
=>245 = 5 +(3.2-1)d
=> 240 = 3.1 ×d
=> 240/3.1 = d
=> d = 77 .41 (approximately)