CBSE NCERT Solutions Chapter 5 Arithmetic Progressions Exercise 5.3 Question 5
5. 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.
Solution:
First term = a = 5
Last term =
Applying formula,
to find sum of n terms of AP, we get
Applying formula,
to find sum of n terms of AP and putting value of n, we get
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