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  1. A sum doubles itself in 16 years, then in how many years will it triple itself; rate of interest being simple
    1. 25 years
    2. 24 years
    3. 48 years
    4. 64 years
    5. None of these
Correct Option: E

Let Principal = Rs. p and Simple Interest = Rs. p

Rate =
SI × 100
Principal × Time

Rate =
p × 100
=
25
% per annum
p × 164

Case II,
Interest = Rs. 2p
∴ Time =
SI × 100
Principal × Rate

Time =
2p × 100 × 4
= 32 year.
p × 25

Second method to solve this question :
Here , n = 2
R =
(n - 1)
× 100%
T

R =
(2 - 1)
× 100
16

R =
25
%
4

R = 6
1
%
4

Now, T =
(n - 1)
× 100
R

Here , n = 3
T =
(3 - 1)
× 100
( 25/4 )

T =
800
= 32 years.
25



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