If the 12th term of an A.P. is - 13 and the sum of the first 4 terms is 24, what is the sum of the first 10 terms?
assuming an AP whose first term is a and the common difference is d
To find: the sum of first 10 terms
Given 12th term is - 13
So, a + 11d = - 13...(i)
Given the sum of first four terms is 24
So 4a + 6d = 24…(ii)
Solving (i) and (ii) we get
a = 9 and d = - 2
we know that the sum of AP is given by the formula:
substituting the values in the above equation
s = 0