Question

A man arranges to pay adept of rupees 3600 in 40 monthly installment which are in a AP when 30 instruments are paid he died leaving one third of the depth and paid find the value of first installment

Answer 1

Hey

HOW r u???

Here u go
first installment = a

common difference between any two consecutive installments =d


Using the formula for the sum of an A.P.
S=n/2 [2a+(n−1)d]

3600=40/2 [2a+(40−1)d]
180= 2a+39d
And 

2400=30/2 [2a+(30−1)d]

160=2a+29d
On solving The above equations we get


d=2 and a=51

Value of 8th installment= 51+(8−1)2 = Rs 65