The annual payment of Rs. 600 in 5 years at the rate of 12% p.a. simple interest will discharge a debt of:

Rs. 3720

Total charge to be paid without interest = 600 × 5 = Rs.3000

Follow this pattern= 

Let Installment =        100    100     100      100    100 = (Total 500)

Interest           =                     12       24        36     48

                                   ————————————————

Total               =              100 + 112 + 124 + 136 + 148 =   620

So, 500 is given as 3000

then, 620 will be 3720