Compound Interest Shortcuts & Tricks for Problem Solving, Techniques

Simple Compound Interest Techniques Short Tricks, Problems and Solutions:

Here we are providing the techniques of Simple Compound Interest. We are explaining the short tricks of Simple Compound Interest. If you are preparing any competitive exam like Bank Exam 2018, SSC Exam 2018, IBPS Exam 2018, RPSC, UPSC and any other SSC Exam. Then it can effective for you. So prepare as according the below explanation: Let take a example-

Suppose Principal= P, Time= t years and Rate= r% per year

Simple and Compound Interest Formulas like-

Short Trick Formula I: 

Annual Interest = P[1+r/100]t

Short Trick Formula II:

Half Yearly Interest: P[1+(r/2)/100]2t = P[1 + r/200]2t

Short Trick Formula III:

Quarterly Compound Interest: P[1+(r/4)/100]4t = P [1+r/400]4t

Short Trick Formula IV:

If Interest rate is r1%, r% and r3% for 1st year, 2nd Year and 3rd Year then

Amount: P[1+r1/100]X[1+r2/100]X[1+r3/100]

Simple Compound Interest Problems with Solutions According Previous Year Papers:

Question 1: Calculate the total time for Rs. 390625 amount to Rs. 456976 at 4% compound Interest Rate??

Solution: Annual Interest (A)= P[1+r/100]t

Putting the values then?

390625 [1+4/100]t = 456976

[1+1/25]t = 456976/390625

[26/25]t= [26/25]4

T= 4 so the time is 4 years.

Question 2: Calculate the least number of complete years in which a sum of money at 20% Compound Interest will be more than doubled???

Solution:  P[1+r/100]t>2P

So 6/5X6/5X6/5X6/5>2 because [6/5]t>2

Then time is t=4 years

Question 3:  If a sum of money at compound interest amounts to thrice itself in three years then Calculate total time when sum of money is 9 times???

Solution: Suppose the sum= Rs. X

Then 3x=x[1+r/100]3 =

Take square of both the sides then

(3)2 = [1+r/100]6

9x=x[1+r/100]6

So the total amount will be 9 times in 6 years

Question 4: If a sum of money placed at compound Interest doubles in 4 years. Calculate the total years in which amount to eight times???

Solution: Suppose X becomes 2x in 4 years

2x becomes 4x in next 4 years

4x becomes 8x in another 4 years

Then 8x becomes 8x in 4+4+4= 12 years

Question 5: Calculate the rate percent compound interest does a sum of money become nine fold in 2 years???

Solution: Suppose that total sum becomes ‘m’ times in ‘t’ years then

R= 100[(m)1/t-1]

R= 100 [(9)1/2-1]= 100(3-1)=200%

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