Question

a sum of rupees 800 is in the former of denominations of Rs.10 and Rs.20 if the total number of notes be 50 find the number of notes in each type

Answer 1

let X be the number of 10 rupees note and Y be the number of 20 rupees note
according to question X + Y = 50 eq1
again 10X + 20Y = 800
X + 2Y = 80 eq 2
subtracting eq 1 and 2
X + 2Y -(X + Y) = 80 - 50
X + 2Y - X -Y = 30
Y = 30 and X = 50 -30 = 20 means 20, 10 rupees note and 30 , 20 rupees note