Question

A sum of Rs 800 is in the form of denominations of Rs 10 and Rs 20 .if the total number of notes is 50 .find the numbers of notes of each types.

Answer 1

let the number of 10 rupee notes be x.
20 rupee notes = 50-x
As per the question,
10x +20(50-x) = 800
10x +1000-20x = 800
10x = 200
x = 20
Thus, Rs 10 notes = 20.
Rs 20 notes = 50-20= 30.

Answer 2

total no. of notes = 50                                        * means multiplication sign 
let no. of notes of Rs 20 = x
hence no. of notes of Rs 10 = 50-x
According to statement
 20*(x) + 10*(50-x)  = 800
20x + 500 - 10x = 800
20x - 10x = 800 - 500
10x = 300
x = 300/10
x = 30
hence no. of notes of Rs 20 = x = 30
           no. of notes of Rs 10 = 50-x = 50-30 = 20