Ramen deposits $\text{Rs. }100$ on the first day of every month in a monthly savings scheme. In this way, he has deposited money for $1$ year. If the rate of simple interest is $6\%$ per annum, then the total amount he will get at the end of the year is

Monthly installment ($P$) $=\text{Rs. }100$
Number of months ($n$) $=12$
Total Principal deposited $=12\times 100=\text{Rs. }1200$
Rate of interest ($R$) $=6\%$ per annum.

The equivalent time for calculating simple interest on a monthly recurring deposit is:

$$T=\frac{n(n+1)}{2\times 12}=\frac{12\times 13}{24}=\frac{13}{2}\text{ months}=\frac{13}{24}\text{ years}$$

Now calculate the total interest:

$$I=\frac{P\times R\times \frac{n(n+1)}{2\times 12}}{100}=\frac{100\times 6\times \frac{13}{24}}{100}=6\times \frac{13}{24}=\frac{13}{4}=\text{Rs. }39$$

Therefore, the total maturity amount received at the end of the year is:

$$\text{Maturity Amount}=\text{Total Principal}+I=1200+39=\text{Rs. }1239$$