CBSE NCERT Solutions Chapter 5 Arithmetic Progressions Exercise 5.3 Question 8
8. Find the sum of first 51 terms of an AP whose second and third terms are 14 and 18 respectively.
It is given that second and third term of AP are 14 and 18 respectively.
Using formula , to find nth term of arithmetic progression, we can say that
These are equations consisting of two variables. We can solve them by the method of substitution.
Using equation (1), we can say that
Putting value of in equation (2), we can say that
Therefore, common difference
Putting value of in equation number (1), we can say that
Applying formula, to find sum of n terms of AP, we get
Therefore, sum of first 51 terms of an AP is equal to 5610.