A sum of Rs 500 is in form of domination of Rs 5 and Rs 10 if the total number of notes is 90 find the number of notes of each type
5 f + 10 t = 500
f + t = 90
f + 2 t = 100
f + 1 t = 90
------------- subtract
t = 10
then f = 80
check
400 +100 = 500
80 + 10 = 90
ok