Question:
The first and the last terms of an AP are 5 and 45 respectively. If the sum of all its terms is 400, find its common difference.
Answer:
Let first term a = 5
last term l = 45
common difference = d
Let total number of terms = n
Given Sum = 400
=> (n/2)(a + l) = 400
=> n(a + l) = 400*2
=> n(5 + 45) = 800
=> 50n = 800
=> n = 800/50
=> n = 16
Now, l = a + (n-1)d
=> 45 = 5 + (16-1)d
=> 45 - 5 = 15d
=> 15d = 40
=> d = 40/15
=> d = 8/3
So, the common difference is 8/3
Not what you are looking for? Go ahead and submit the question, we will get back to you.
