Compound Interest
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A man borrows money at 3% per annum interest payable yearly and lend it immediately at 5% interest (compound) payable half-yearly and thereby gains ₹ 330 at the end of the year. The sum borrowed is
-
₹ 17000
-
₹ 16500
-
₹ 15000
-
₹ 16000
D.
₹ 16000
Shortcut Method:Go with option, say 'option (d)' sum borrowed ₹16000
If principal = ₹16000
Case I, When given on 3% interest p.a. then interest would be 3% on 16000 = ₹480
Case II, When given on 5% interest (compound) payable half-yearly then interest would be
Total interest = (400 + 410) = ₹ 810
Difference of interest = ₹ (810 - 480) = ₹ 330
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A man invested a sum of money at compound interest. It amounted to Rs. 2420 in 2 years and to Rs. 2662 in 3 years. Find the sum.
-
Rs. 1000
-
Rs. 2000
-
Rs. 5082
-
Rs. 3000
B.
Rs. 2000
Rate of interest:
Now,
A man spends ₹ 1800 monthly on an average for the first four months and ₹ 2000 monthly for the next eight months and saves ₹ 5600 a year. His average monthly income is
-
₹ 2000
-
₹ 2200
-
₹ 2400
-
₹ 2600
C.
₹ 2400
Total Spendings of man in a year
= Rs. (4 x 1800 + 8 x 2000)
= Rs. (7200 + 16000)
= Rs. 23200
Savings = ₹ 5600 a year.
Total annual income = (23200 + 5600) = ₹ 28800
∴ Average monthly income = 
A sum amounts to Rs. 2,916 in 2 years and to Rs. 3,149.28 in 3 years at same rate of compound interest. The sum is
-
Rs. 2500
-
Rs. 2400
-
Rs. 2250
-
Rs. 2000
A.
Rs. 2500
Interest = 3,149.28 - 2,916 = 233.28
Now,
A sum of money at compound interest amounts to thrice itself in 3 years. In how many years will it be 9 times itself?
-
9
-
27
-
6
-
3
C.
6
'X' becomes '3X' in 3 years,
∴ '3X' becomes ' 9X' in (3 + 3) = 6 years.
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