Question

Mohan deposits Rs. 500 in the first month, Rs. 550 in the second month, Rs. 600 in
the third month and so on. Find the total deposit at the end of 5 years
​

Answer 1

Answer :-

Here, we are given first term i.e. 500 , then we have common difference of Rs. 50.

We can calculate number of months he deposited his money. According to the question, he deposited money for 5 years and in each month, so total months = 5 × 12 = 60 months -

So, now we have -

• a = 500
• d = 50
• n = 60

$\sf S_n = \dfrac{n}{2} [ 2a + ( n - 1 ) d ]$

$\sf = \dfrac{60}{2} [ 2 \times 500 + ( 60 - 1 ) 50 ]$

$\sf = 30 [ 2 \times 500 + (59)50]$

$\sf = 30 [ 2 \times 500 + 2950 ]$

$\sf = 30 [ 1000 + 2950 ]$

$\sf = 30 [ 3950 ]$

$\sf = 118500$

Total money he deposited at the end of 5 years = Rs. 118500