# Simple and Compound Interest ( 16 to 20 )

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Simple and Compound Interest ( 16 to 20 ):

# APTITUDE QUESTIONS (SIMPLE AND COMPOUND INTEREST):

16. At what rate of percent of simple interest will a sum of money double itself in 12 years?

A)    17/2 %

B)    19/2%

C)    13/4%

D)    25/3%

E)    None of these

Explanation:

Let sum = x. Then, S.I. = x

R = (100 * S.I. / T * P)

Therefore, R = (100 * x / 12 * x) = 25/3%

17. If a sum of money at simple interest doubles in 6 years, it will become 4 times in?

A)    18 years

B)    16 years

C)    14 years

D)    12 years

E)    None of these

Explanation:

Let sum = x. the, S.I. = x

Therefore, R = (100 * x / 6 * x) = 50/3%

Now, sum = x, S.I. = 3x, R = 50/3%

T = 100 * 3x/ x* 50/3 = 18 years

18. There is 50% increase in an amount in 5 years at simple interest. What will be the compound interest of Rs.15000 after 3 years at the same rate?

A)    Rs.4965

B)    Rs.2160

C)    Rs.3972

D)    Rs.6340

E)    None of these

Explanation:

Let P = 100. Then, S.I. = Rs.50 and T = 5years

Therefore, R = 100 * 50 / 100 * 5 = 10%

Now, P = Rs.15000, T = 3 years, R = 10%

Therefore, C.I. = Rs. [15000 * {(1 + 10/100)3 – 1}] = Rs. (15000 * 331/1000) = Rs.4965

19. A sum of money invested at compound interest amounts to Rs.4624 in 2 years and to Rs.4913 in 3 years. The sum of money is?

A)    Rs.4096

B)    Rs.4260

C)    Rs.4335

D)    Rs.4360

E)    None of these

Explanation:

S.I. on Rs.4624 for 1 year = Rs. (4913 – 4624) = Rs.289

Therefore, Rate = (100 * 289 / 4624 * 1) = 25/4%

Now, x (1 + 25/4 * 100)2 = 4624 or x * 17/16 * 17/16 = 4624

Therefore, x = (4624 * 16/17 * 16/17) = Rs.4096

20. At what rate of percent per annum will the simple interest on a sum of money be 2/5 of the amount in 10 years?

A)    6%

B)    17/3%

C)    4%

D)    20/3%

E)    None of these

Explanation:

Let sum = x. Then, S.I. = 2x/5, T = 10 years

Therefore, R = (100 * 2x / x * 5 * 10) = 4%