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Amount=Rs.21648.64
Compound Interest = Total amount – Principal
= 21648.64 – 20000
= Rs. 1648.64
If the simple interest for certain sum for 2yrs at the annual rate of interest R% is SI. Then,
Compound interest (CI) = SI (1+r/200) (no. of years =2)
5). If the simple interest for a certain sum for 2 yr at 5%pa is 200, then what will be the compound interest for same sum for same period and the same rate of interest?
Sol:
Si =200 r=5%
Ci =200(1+5/200) =200*(205/200) =205
If a certain sum at compound interest becomes x times n_{1}^yr and y times n_{2}^yr then,
X^{1/N1} = Y^{1/N2}
6). If an amount at compound interest becomes twice in 5yr, then in how many years, it will be 16 times at the same rate of interest?
2^{1/5 }= 16 ^{1/x2}
=2^{4*1/x2}
1/5 = 4/x_{2}
X_{2} = 5*4 =20yrs
If a certain sum at compound interest amounts to A_{1} in n yrs and A_{2} in (n+1) yrs,
then
Rate of compound interest =(A_{2} – A_{1})/A_{1} *100%
Sum = A_{1} (A_{1} /A_{2})^{n}
7). A sum of money invested at compound interest amounts to 800 in 2yr and 840 in 3yrs .Find the rate of interest and the sum.
A_{1} =800 ; A_{2 }=840,
Rate of interest = (840800)/800 *100% =40/8 =5%
Sum = 800 *(800/840)^{2} =320000/441 = Rs.725.62
If the populations of a city P and it increases with the rate of R% per annum, then
8). The population of a city A is 5000. It increases by 10% in 1^{st} year. It decreases by 20% in the 2^{nd} yr because of some reason. In the 3^{rd} yr, the population increases by 30%. What will be the [population of area A at the end of 3yrs?
=5000(1+10/100)(120/100)(1+30/100)
= 500*(11/10)*(4/5)*(13/10) = 5720
Difference between ci and si 2yr =pr^{2} /100^{2 }
9). The difference between c.i and s.i for 2yr at the rate of 5% per annum is 5 .then the sum
5 = p (5/100)^{2} = Rs.2000
Rate of interest (no .of years =2)
(for only ci)
2% = 4.04%
3% = 6.09%
4% = 8. 16%
5% = 10.25%
6% = 12.36%
7% = 14.49%
8% = 16.64%
9% = 18.81%
10%= 20.00
+ 1.00 =21%
10). What is the Compound interest for Rs. 1500 at 5% rate of interest for 2 years?
1500*(10.25/100) =153.75
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