# 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——–>?

$\frac{550\times&space;576}{55}=5760$

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=$\frac{PTR}{100}=\frac{38400\times&space;10\times&space;3}{100}=11520$

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+$\frac{20\times&space;20}{100}=44$%

Scheme A=15% S.I

Assume principal is 100

$S.I=\frac{PTR}{100}=\frac{100\times&space;2\times&space;15}{100}=130$%

44%——–>2860

100%——–>?

$\frac{2860\times&space;100}{44}=6500$

$\frac{6500\times&space;100}{130}=50,000$

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

$2\times&space;\frac{9}{10}$    :        $3\times&space;\frac{6}{5}$

1              :            2

$\frac{1}{1}\times&space;100=100$% change