Question

Q4.The value of a machine depreciates every year at the rate of 20% of its
value at the beginning of the year. The machine was purchased for Rs.2,50,000
and its value was Rs. 1,28,000 when it was sold after using it for a number of
years. Find the number of years that the machine was used.

Answer 1

Let the required number of years be n

∴ Value of machine after n years = Its value when new (1−

100

r

)

n

[Using the concept of compound interest]

Given that the initial value of the car is Rs.250000 and its value after n years is Rs.128000

∴ Rs.128000=Rs.250000(1−

100

20

)

n

⇒

Rs.250000

Rs.128000

=(

100

80

)

n

=(

5

4

)

n

On simplifying, we get :

(

5

4

)

3

=(

5

4

)

n

⇒n=3 years