Question

A sum of rs 500 is in the form of denominations of rs 5 and rs 10. If the number of notes is 90,find the number of notes of each type.

Answer 1

let
5 rs. note=A,
10rs note=B,

then
A+B=90,..........eq(1),

5A+10B=500,

A+2B=100,.......eq(2),

subtract eq(1) from eq(2), we get

B=10,

then

A+10=90,

A=80

Answer 2

let the no of 5 and 10 rs coin be x and y
Now
A/Q
x+y=90
x=90-y
and
5x+10y=500
5(x+2y)=500
x+2y=100
90-y+2y=100
y=10
and x=90-10=80