NCHMCT JEE 2015 Question Paper with solutions for online practice

Question : 8 of 200

Marks: +1, -0

A sum of 125 doubles in 5 years, the interest being compounded annually. In how many more years will it get additional interest of 250?

Solution:

A = P

(1+r/{100})^t

⇒ 2P =

P(1+r/{100})^5

⇒ 250 =

125(1+r/{10})^5

⇒ 2 =

(1+r/{100})^5

... (i)
Now, A = P

(1+r/{100})^n

[Since A = CI + P = 375 + 125 = 500]
⇒

{500}/{125}

(1+r/{10})^n

⇒ 4 =

(1+r/{100})^n

⇒

(1+r/{00})^n

(2)^2

[(1+r/{10})^5]^2

⇒

(1+r/{100})^{10}

= n = 10 years
∴ Required no. of years = 5.

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