Question

a sum of rs 7260 is paid off in 20 instalment such that each instalment is rs 20 more than the preceding instalment . calculate the value of the first instalment

Answer 1

This needs arithmetic progression, and here we go.
here, the common difference is Rs 20, right!
totally, 20 installments, right!
then, SUM OF 20 = S20 = 7260.
S20 = n/2 [2a + (n-1)d]
Here, n = 20, as the money is shared with 20.
therefore, S20 = 20/2 [2a+(20-1)20]
7260/10 = 2a+380
726 = 2a+380
726-380 =2a
2a= 346.
a = 173.
Hope this will help you.

Answer 2

number of instalments(n)=20
common difference(d)=20
sum=7260
7260=$\frac{n}{2}(2f+(n-1)d)$
[tex]7260*2=20(2f+19*20) \\ \\ 14520=20(2f+380) \\ \\ \frac{14520}{20} =2f+380 \\ \\ 726=2f+380 \\ \\ f+190=363 \\ f=363-190=173 \\ \\ [/tex]

first instalment = 173 rs