A sum of money triples itself in 20 years. The rate of interest is:

1. 20%

2. 10%

3. 5%

4. 15%

A sum of money earns simple interest equal to 0.5 times the sum in 10 years; the rate of interest per annum is :

1. 20%

2. 10%

3. 5%

4. none of these

Manoj invested ₹ 8,000 for 10 years at 10% p.a. simple interest. The amount at the end of 2 years will be :

1. ₹ 9,600

2. ₹ 9,800

3. ₹ 16,000

4. None of these