If Ramesh Kumar has an R.D. in a post office, he has to deposit:

1. an amount only once

2. the same amount every month

3. a decreasing amount every month

4. an increasing amount every month

In an R.D., the maturity value is the sum of the total amount deposited and the interest. If P is the amount deposited every month for n months and R is the rate of interest, then interest I is equal to:

1. $P \times \dfrac{n}{12} \times \dfrac{R}{100}$

2. $P \times \dfrac{n(n - 1)}{12} \times \dfrac{R}{100}$

3. $P \times \dfrac{n(n + 1)}{2 \times 12} \times \dfrac{R}{100}$

4. $P \times \dfrac{n}{2 \times 12} \times \dfrac{R}{100}$

Naveen deposits ₹800 every month in a recurring deposit account for 6 months. If he receives ₹4,884 at the time of maturity, then the interest he earns is:

1. ₹84

2. ₹42

3. ₹24

4. ₹284

Mr. Anuj deposits ₹500 per month for 18 months in a recurring deposit account at a certain rate. If he earns ₹570 as interest at the time of maturity, then his matured amount is:

1. ₹(500 x 18 + 570)

2. ₹(500 x 19 + 570)

3. ₹(500 x 18 x 19 + 570)

4. ₹(500 x 9 x 19 + 570)