Step 1 :

(a)

Total amount .

The rate of interest is

Since the amount is doubled,

Formula for continuous compounding is

Substitute and in above equation.

Apply logarithm on each side.

Use the formula :

The time required for the amount to double is sec.

Step 2 :

(b)

Since the amount is tripled,

Formula for continuous compounding is

Substitute and in above equation.

Apply logarithm on each side.

Use the formula :

The time required for the amount to triple is sec.

Solution :

(a) The time required for the amount to double is sec.

(b) The time required for the amount to triple is sec.