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Simple Interest Shortcut Formulas

Simple Interest Shortcut Formulas With Examples

  1. Simple Interest = PTR/100, (P=Principle Amount, T=Time, R=Rate).
  1. The annual payment that will discharge a debt of ARs/- in ‘t’ years at the rate of interest r% per annum.

Then Payment = (100A) / [(100t )+[(rt(t-1)]/2].

  1. Sum = (100I)/(r1t1+r2t2+….)

If a sum of money become x times in t years at simple interest. Then Rate = [[100(x-1)]/t]%.

  • Principle = 100A/100+RT.
  1. Sum= [Interest difference/(r1t1-r2t2)]*100.
  1. If a sum amounts to A1 in t1 years and A2 in t2 years.

Then Rate of Interest = 100[A1-A2]/ [A1T2-A2T1].


Simple Interest Shortcuts With Examples

 Problem 1: Simple Interest on an amount after 24 months at the rate of 2% per quarter is 960. What is the sum?

Sol: R= 2% per quarter.
=(2% * 4)per  year. = 8 % p.a.
Simple Interest (S.I.)=1st year+ 2nd year=  8%+ 8%= 16%
Here understand the logic i.e.  16% amount à960
Then (sum means 100%)so for 100% à?
With cross multiplication, Sum= 100*960/16=6000.

Problem 2: The simple interest of money is Rs.300 after 5 years. In next 5 years, If the principle is tripled what will be the total interest at the end of the 10th year?

Sol: 1st 5 years, SI = 300.
Next 5 years à New P| = 3P
New SI| = 3 SI
= 3 *300 =900.
Total Interest = 300+900. = 1200.

Problem 3: Varun borrows 1500 Rs. From a lender. He pays interest at the rate of 12% p.a. for one loan and rate of 14 % for another loan. How much does he borrow at 12% p.a? If the interest paid at the end of the year is 186 Rs.

Sol: Given, SI 1 + SI 2=186.    P1 is 12% p.a.        P2 is at 14% p.a.
And  P1 +P2= 1500  àequation 1
From above information 12%of P1 +14% of P2 =186      àequation 2.
Solve these 2 equations 1&2 we get P2=300.
And P1 = 1200.


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