Question

lalit mother gave him some 10rupees note and some 5 rupee note amounting rupees 190.if mother had interchanged the notes given to me,i would have 185 rupee with me. find the number of 10 & 5 rupee notes given to lalit by his mother

Answer 1

let be the 10rupees not x and 5rupees not be y so that 10x+5y=190 which is our first equation now by interchanging the notes we get our second equation 5x+10y=185.Now eliminate either x or y by making same comultiplier of x or y and this can be done by multiplying second equation with 2 so that second equation would be now 10x+20y=370.Now by substracting this equation from our first equation we get -15y=-180 so y=12,now by putting this value of y into the first equation we get x=13