Compound Interest Part 8

Problem 1: An equal principal was invested in two banks first offering 15% simple interest and the second offering compound interest of 20% if the difference of interest from both banks after 3 years was Rs.417. Find the principal invested in each bank?

Solution:

Simple Interest=15*3=45%

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

44+20+\frac{44\times 20}{100}=72.8%

72.8-45=27.8%

27.8%——–>417

100%———->?

\frac{417\times 100}{27.8}=1500

Problem 2: Simple interest on a principal of 2 years is 108.80 and compound interest on same principal for the same time period and rate of interest is  RS 115.60. Find the rate of interest?

Solution: Simple interest on a principal of 2 years is 108.80

Note: Simple interest is same for every year

\frac{108.80}{2}=54.40

54.40 S.I for the first year

54.40 S.I for the second year

Compound interest on same principal for the same time period and rate of interest is  Rs.115.60

115.60-108.80=6.8

1st year C.I is 54.40

2nd year C.I is 54.40+6.8

54.40|  54.40|  6.8

54.40\times \frac{x}{100}=6.8

x= \frac{6.8\times 100}{54.40}=12.5%

 

Problem 3: A sum of Rs.2592 was invested in two banks the first bank offers C.I of 16\frac{2}{3}% compounded annually whereas the second bank offers S.I of 12\frac{1}{2}%. Find the difference between S.I and C.I of 2 years 6 months?

Solution:

C.I is 16\frac{2}{3}%=\frac{1}{6}

S.I is 12\frac{1}{2}%=\frac{1}{8}

S.I=2592\times \frac{1}{8}\times \frac{5}{2}=810

C.I== 432+432+216+72+36+36+6 = 1230

Difference between C.I and S.I = C.I – S.I = 1230-810=420

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