Word Problem 10
Problem 10: On a certain investment simple interest is applied at certain rate. The amount doubles in 20 years term. After how many years the amount will be quadrupled ?
Here are situations of two cases, First case is given as 20 years period, and second case duration is to be found in which interest amount will be four times !
In 20 years period
P = Principal amount ( Amount in the beginning or investment amount)
I = Interest on principal amount
A= total amount at the end, which is sum of initial amount and interest incurred.
According to condition, amount ‘A’ doubles in 20 years i-e
Put in relation (1), this value of ‘A’, we get
It means interest will be equal to principal amount in 20 years !
In second case we want amount ‘A’ to become four times i-e
Put this value in eq (1) above, we get;
Now equation (2) says ‘I’ the interest will be equal to ‘P’ in 20 years i-e P is equal to interest of 20 years or we can say ‘P’ is the amount of 20 years. So we can take
So we put P = 20 years in eq(3)
It means after interest of 60 years the amount will be 4 times !
Or we can say in 20 years the amount will be quadrupled