Question

the sum of 500 is in the form of denomination of rupees 5 and 10 the total number of note is 90 find the note of each type

Answer 1

Total number of notes = 90.
If number of ₹5 notes = x
and number of ₹10 notes = y

then the first equation will be,
x + y = 90......(1)
(meaning sum of notes is 90)

and the second equation will be,
5x + 10y = 500.....(2)
(means the note number * note value)

from (1) we get :-
x + y = 90 => y = 90 - x

substituting value of x in (2)
5x + 10y = 500 => 5x + 900 - 10 x = 500
=> -5x = -400 => x = 80

Substituting value of x in (1)
x + y = 90 => 80 + y = 90 => y = 10

So the number of ₹5 notes = 80
and the number of ₹10 notes = 10