SIMPLE INTEREST
Interest:-
Interest is the extra money paid by the borrower to owner (lender) as a form of compensation for the used of the money borrowed calculated on the basis of the principal.
Time:-
This is the duration for which money is lend / borrowed
Amount :-
The addition of principle and simple interest is called the amount .
Rate of Interest:-
It is the rate at which the interest charge on principle.
Formula
SI = P*R*T/100
SI -simple interest
P - principle
R - rate of interest
T - time period
Amount=Simple Interest + Principle
E.g.1.
A sum of money at simple interest n1 itself in t1 year. It will becomes n2 times of itself in (if rate of interest is constant)
E.g. 2.
A principle amount become double in 8 years calculate the rate of interest ?
Solution:-
Let the principle x Rs.
Since it becomes double in 8 year so Si in
8=x Rs.
SI=P*R*T/100
x=x*R*8/100
R=12 and 1/2
E.g. 3.
A principal amount become 3 times in 12 years calculate the rate of interest?
Solution:-
Let the principal amount be xRs
since it become triple in 12 years so
SI in 12 years=2x Rs.
SI=P*R*T/100
2x=x*R*12/100
R=16and 2/3
E.g. 4.
A some of money becomes 7/6 of itself in 3 year at a certain rate of simple rate of interest. The rate of interest per annum is :
Let the principal 6P
Hence , Amount =6P*7/6 = 7P
SI=7P-6P=P
Times=3years
SI=P*R*T/100
P=6P*3*R/100
R=5 and 5/9
Short trick :-
E.g. 5.
A sum of Rs. 1550 was lent by partly at 5% and partly 8% simple interest. The total interest received after 3 years is Rs.300. The ratio of money lent at 5% to that at 8% is:
Solution:-
Avg rate of interest
= 300/1550*100/3
200/31%
by using mixture and alligation
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