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- Question
- The population of a city increases at the rate of 5% pa. If the present population of the city is 185220, then what was its population 3 yr ago?
Options- A. 181500
- B. 183433
- C. 160000
- D. 127783
- Correct Answer
- 160000
ExplanationGiven, P = 185220 R = 5% (increases) and n = 3 yr
According to the formula,
Population n yr ago = P/(1 + R/100)n
= 185220/(1 + 5/100)3
= 185220/[(21/20) x (21/20) x (21/20)]
= [185220 x 20 x 20 x 20] / [21 x 21 x 21]
= 20 x 20 x 20 x 20
= 160000 - 1. If ? 3000 amounts to ?4329 at compound interest in a certain time , then ? 3000 amounts to what inhalf of the time?
Options- A. ? 3400
- B. ? 3600
- C. ? 38000
- D. ? 3520 Discuss
- 2. A borrowed sum was paid in the two annual installments of ? 121 each. If the rate of compound interest is 10% pa, what sum was borrowed?
Options- A. ? 217.80
- B. ? 210
- C. ? 220
- D. ? 200 Discuss
- 3. The difference between compound and simple rates of interest on ? 10000 for 3 yr at 5% per annum is
Options- A. ? 76.25
- B. ? 76.75
- C. ? 76.50
- D. ? 76 Discuss
- 4. What is the difference between compound interest and simple interest for 2 yr on the sum of ? 1250 at 4% pa?
Options- A. ? 3
- B. ? 4
- C. ? 2
- D. ? 8 Discuss
- 5. The compound interest on ? 30000 at 7% pa for a certain time is ?4347. The time is
Options- A. 2 yr
- B. 2.5 yr
- C. 3 yr
- D. 4 yr Discuss
- 6. A sum of ? 400 amounts to ? 441 in 2 yr. What will be its amount, if the rate of interest is increased by 5%?
Options- A. ? 484
- B. ? 560
- C. ? 512
- D. ? 600 Discuss
- 7. The cost price of an LCD TV set is ? 100000. If its price value depreciates at the rate of 10% pa. then what will be the price at the end of 3 yr?
Options- A. ? 80000
- B. ? 85000
- C. ? 90000
- D. ? 72900 Discuss
- 8. A sum, at the compound rate of interest, becomes 2 1/ 2 times in 6 yr. The same sum becomes what times in 18 yr?
Options- A. 5/2
- B. 25/4
- C. 125/8
- D. 625/16 Discuss
- 9. If the difference between the compound interest and simple interest on a sum of money at 5% pa for 2 yr is ? 16, then find the simple interest?
Options- A. ? 840
- B. ? 932
- C. ? 520
- D. ? 640 Discuss
- 10. The compound interest is ? 6.40 more than the simple interest, if a sum is lent for 2 yr at 8% compound interest. Find the sum.
Options- A. ? 1800
- B. ? 10000
- C. ? 800
- D. ? 1000 Discuss
Compound Interest problems
Search Results
Correct Answer: ? 3600
Explanation:
Let rate = R% and time = n yr
Then, 4320 = 3000(1+R/100)n
? (1+R/100)n = 4320/3000 = 1.44
? (1 + R/100)n/2 = ?1.44 = 1.2
? Required amount for n/2 yr
= 3000(1+ R/100)n/2
= 3000 x 1.2 = ? 3600
Correct Answer: ? 210
Explanation:
According to the question,
Borrowed sum = [121/{1/(1 + 10/100)}] + 121/(1 + 10/100)2
= 121/(11/10) + 121/{(11/10) x (11/10)]
=110 + 100
= ? 210
Correct Answer: ? 76.25
Explanation:
Required difference = P(R/100)2 x [(300 + R)/100]
= 10000(5/100)2 (305/100)
= 76.25
Correct Answer: ? 2
Explanation:
Given, P = ? 1250, n = 2 yr and R = 4%
According to the formula,
Difference between compound interest and simple interest = PR2/1002
? Required difference = (1250 x 4 x 4)/(100 x 100) = ? 2
Correct Answer: 2 yr
Explanation:
Given, CI = ? 4347, P = ? 30000 and R = 7%
By formula, CI = P[(1 + R/100)n - 1 ]
? 4347 = 30000 [(1+7/100)n - 1]
? (107/100)n = (4347/30000) + 1
? (107/100)n = 34347/30000 = 11449/10000
? (107/100)n = (107/100)2
? n = 2
Correct Answer: ? 484
Explanation:
According to the given condition.
441 = 400 (1 + R/100)2
? 441/400 = (1 + R/100)2
? (21/20)2 = (1 + R/100)2
? 21/20 = 1 + R/100
? (21/20) - 1 = R/100
? R/100 = 1/20
? R = 5%
? new rate = 5 + 5 = 10%
? Amount = 400 (1 + 10/100)2
= 400 x (11/10) x (11/10)
= ? 484
Correct Answer: ? 72900
Explanation:
Given P = ? 100000, R = 10%, n = 3 yr
According to the formula,
Price of LCD TV set after 3 yr. = P(1 - R/100)n
= 100000 (1 - 10/100)3
= 100000(90/100)3
= 100000 x (9/10) x (9/10) x (9/10)
= ? 72900
Correct Answer: 125/8
Explanation:
If sum is P, then P becomes 5P/2 in 6 yr.
5P/2 becomes 25P/4 in 12 yr.
25P/4 becomes 125P/8 in 18 yr.
The sum becomes 125/8 times in 18 yr.
Correct Answer: ? 640
Explanation:
Given, CI - SI = 16, R = 5%, n = 2 yr and SI = ?
According to the formula,
CI - SI = (SI x R)/200
? 16 = (SI x 5)/200
? 16 = SI/40
? SI = ? 640
Correct Answer: ? 1000
Explanation:
Here, D = ?6.40, R = 8% and n = 2 yr
Then, according to the formula,
Difference between compound interest and simple interest
D = PR2 / 1002
? 6.40 = P x 64/10000
? P = ? 1000
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