# Formulas To Solve Simple Interest Problems

## Simple Interest Formulas

Simple Interest is the rate at which we lend or borrow money. In simple terms, when a lender lends money to a borrower, the borrower has to pay an extra amount of money to the lender.  This extra amount of money is called interest. The interest on a sum borrowed for a certain period is called simple interest.

• Simple interest is calculated by multiplying the daily interest rate by the principal by the number of days that elapse between payments.
• This type of interest usually applies to short-term loans,.
• Basic Formula PxRxT/100 ## Formula for Simple Interest

### Simple Interest Formulas

SI = P*r*t/100

Where,

P = money borrowed or lent out for a certain period(principal)

r = rate of interest

t = time period for which the amount is lent

1. Principal = 100* SI/ R * T
2. Rate = 100* SI/ P * T
3. Time = 100* SI/ R * P

### To get total amount of money

Amount = Principal + Interest

A = P + I

## Formulas based Questions on Simple Interest

### Example 1

Find the simple interest on Rs. 65,000 at 6(2/3)% per annum for a period of 9 months?

Options
(A) 3520
(B) 3250
(C) 2350
(D) 5320

Explanations
Principle = 65,000
Rate = 6$\frac{2}{3} \$
Time = 9 months

Principle = 65,000

Rate = $\frac{20}{3} \$

Time =$\frac{3}{4} \$

S.I = $\frac{P*R*T}{100} \$

= Rs. [65000×(20/3)×(3/4)×(1/100)]

= 3250

### Example 2

What sum of money will amount to Rs. 520 in 5 years and Rs. 568 in 7 years at simple interest?

Options
(A) 350
(B) 400
(C) 550
(D) 500

Explanations

Amount in 5 years = Rs 520
Amount in 7 years = Rs 568

2 years S.I = 568-520 = 48
Simple Interest for 1 years = latex \frac{48}{2} \ [/latex] = 24

5 years amount = Rs 520
For 1 years = 5*24 = 120

P = A – S.I = 520-120
P = 400