*Tips, Tricks& Results for Simple Interest-2*

*The purpose of this article is to provide you with some useful tips and tricks that you can use for Simple Interest questions. Various applications and formulas based on this concept are explained here. *

*Simple Interest Tips, Tricks, and Results: Tooltip 1 *

Change in Simple Interest when time changes from T_{1 }to T_{2} is given by the formula:

Change in Simple Interest when principal changes from P_{1 }to P_{2} is given by the formula:

Change in Simple Interest When rate of interest changes from r_{1}to r_{2} is given by the formula:

**Example: **Simple interest on Rs 200 increases by Rs 50 when time increases by 5 years. Find rate percent per annum.

**Example: **If the SI on Rs 1000 be more than the interest on 2000 by Rs 20 in 4 years, find the rate per annum.

**Solution:** When principal changes from P_{1}to P_{2}

*Simple Interest Tips, Tricks, and Results: Tooltip 2*

If a person deposits A_{1} amount at r_{1}% per annum and amount A_{2 }at r_{2}% per annum, then the rate of interest for the whole sum is {(A_{1}r_{1} + A_{2}r_{2})/(A_{1}+A_{2})}

**Example: **A man deposits Rs.1000 at 4% per annum and Rs 2000 at 5% per annum, find the rate of interest for the whole sum.

**Solution: **

*Method-1:*

Using the formula for, Simple Interest (SI) = {(P x R x T)/100}

X = {(1000 x 4 x 1)/100} = 40

Y = (2000 x 5 x 1)/100 = 100

Total interest = 100+40=Rs. 140

Total principal =1000+2000=Rs.3000

Using the formula:

140 = {(3000 x R x 1)/100}

R = 14/3%

*Method-2:*

Applying above concept {(A_{1}r_{1} + A_{2}r_{2})/(A_{1}+A_{2})}, the rate of interest is

[{(1000 x 4) + (2000 x 5)}/(1000 + 2000)]

= 14000/3000

14/3%

*Simple Interest Tips, Tricks, and Results: Tooltip 3*

A certain amount is invested for certain time but at different rates. When rate per annum is r_{1} the amount becomes x_{1} but at rate r_{2 }per annum, the amount becomes x_{2} .

Time, t, is given by the formula:

t = {(x_{1} – x_{2})/(x_{2}r_{1} – x_{1}r_{2})}*100

### Simple Interest (Complete Lesson): Table of Contents

**Concept Articles****Exercise **

**Practice Tests **