Compound Interest Part 9

Problem 1: When a certain principal is invested at 16.66% compound interest instead of 12.5% per annum for 2 years the interest is 550 more. Find the principal?

Solution:

12.5% ——–>\frac{1}{8}——–>64

16.66%——–>\frac{1}{6}——–>36

LCM Of 64 and 36 is 576 is principal

                     

72+72+9=153                                             96+96+16=208

208-153=55

55———->550

576——–>?

\frac{550\times 576}{55}=5760

Problem 2: Raju took Rs.38400 from Rama at 10% rate of SI and give it to Surya who gives 12.5% rate of C.I compounded annually. If Raju gives the money to Surya for 3 years and returns to Rama immediately. Find the profit of Raju?

Solution:

S.I=\frac{PTR}{100}=\frac{38400\times 10\times 3}{100}=11520

4800*3=14400

600*3=1800

14400+1800+75=16275

16275-11520=4755

Problem 3: A man invested a sum of money in scheme A, at the rate of 15% per annum for S.I, at the end of two years the amount received by him is invested in scheme B at 20% per annum for C.I. If the interest received by him from scheme B at the end of the second year is RS. 2860, then find the sum invested by a man in the beginning?

Solution:

Scheme B=20% C.I

20+20+\frac{20\times 20}{100}=44%

Scheme A=15% S.I

Assume principal is 100

S.I=\frac{PTR}{100}=\frac{100\times 2\times 15}{100}=130%

44%——–>2860

100%——–>?

\frac{2860\times 100}{44}=6500

\frac{6500\times 100}{130}=50,000

Problem 4: A and B have an amount in 2:3 if A buy a car from his money whose price is depreciated by 10% whereas B invested that money in the bank which gives C.I at the rate of 20% per annum. Find the total percentage change in the total amount?

Solution:

10%=\frac{1}{10}–  ——>  Depreciates —–>  \frac{9}{10}

20%=\frac{1}{5}    ———> Increases  ——-> \frac{6}{5}

A             :                B

2              :                3

2\times \frac{9}{10}    :        3\times \frac{6}{5}

1              :            2

\frac{1}{1}\times 100=100% change

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