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2023

Mathematics

67ca00ce0c643c71d77dee1f

At simple interest, a man made a deposit of some money in the bank. The amount in his bank account after 10 years is three times the money deposited. If the interest rate stays the same, after how many years will the amount be five times the money deposited?

A.

15 years

B.

25 years

C.

20 years

D.

30 years

Correct Answer: 20 years

Explanation

Amount (A) = Principal (P) + Interest (I) i.e. A = P + I 1 = PTR/100 A = 3P; T = 10 years (Given) Since A = P + I ⟹3P=P+P×10×R/100 ⟹3P=P+10PR/100 ⟹3P=P+PR/10 ⟹3P−P=PR/10 ⟹2P=PR/10 ⟹2P/1=PR/10 ⟹ PR = 20P ∴ R = 20% Since the rate stays the same A = 5P; R = 20%;T =?; A =P + I ⟹5P = P + (p × T × 20)/100 ⟹5P − P = (2PT)/10 ⟹4P = (2PT)/10 ⟹2P = PT/10 ⟹ PT = 20P ∴ T = 20 years

Amount (A) = Principal (P) + Interest (I) i.e. A = P + I 1 = PTR/100 A = 3P; T = 10 years (Given) Since A = P + I ⟹3P=P+P×10×R/100 ⟹3P=P+10PR/100 ⟹3P=P+PR/10 ⟹3P−P=PR/10 ⟹2P=PR/10 ⟹2P/1=PR/10 ⟹ PR = 20P ∴ R = 20% Since the rate stays the same A = 5P; R = 20%;T =?; A =P + I ⟹5P = P + (p × T × 20)/100 ⟹5P − P = (2PT)/10 ⟹4P = (2PT)/10 ⟹2P = PT/10 ⟹ PT = 20P ∴ T = 20 years
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