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1) A sum of money becomes 8 times of itself in 3 yrs at Compound interest. The rate of interest is:A) 100 B) 50 C) 10 D) 12
2) The difference between simple interest and compound on $ 1500 for one year at 20% per annum compounded half-yearly is:A) $300 B) $305 C) $320 D) $315
Answer & Explanation
Answer: $315 (S.I. = $ 1500 x20 x 1/100 = $ 300
C.I. = $ 1500 x (1 + 10/100)2 - 1500 = $1500 * (11/10 * 11/10) -1500 = $1815
Difference = $. (1815 - 1500) = $ 315.
)
3) The compound interest on a certain sum for 2 years at 10% per annum is $ 630. The simple interest on the same sum for double the time at half the rate percent per annum is:A) $550 B) $600 C) $625 D) $650
Answer & Explanation
Answer: $600 (Let the sum be Rs. P.
Then, P (1 + 10/100)2 - P = 630
P *( (11/10)2 - 1 ) = 630
P = 630 x 100/21 = 3000.
Sum = $. 3000.
So, S.I. = $3000 x 5/100 x 4 = $600
)
4) There is 50% increase in an amount in 5 years at simple interest. What will be the compound interest of $10,000 after 3 years at the same rate?A) $3310 B) $3210 C) $3510 D) $3110
Answer & Explanation
Answer: $3310 ( Let P = $100. Then, S.I. $ 50 and T = 5 years.
R = 100 x 50/100 * 5 = 10% p.a.
Now, P = $10000. T = 3 years and R = 10% p.a.
C.I= $ 10000 x ( 1 + 10/100)3 - 1 ) - 1
= 10000 x 331 /1000= $3310
)
5) A sum of money invested at compound interest amounts to $800 in 3 years and $880 in 4 years, What is the rate of interest per annum?A) 5% B) 9% C) 10% D) 8%
Answer & Explanation
Answer: 10% (Interest on $800 for 1 yr = $(880-800) = $80
Therefore, Rate=(100*80/800*1)%=10%
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