54 nickels and 27 dimes
1 dime = 10 cents = $0.1
1 nickel = 5 cents = $0.05
setting up 2 equations
let n = amount of nickels and d = amount of dimes, then
n + d = 81 → (1)
0.05n + 0.1d = 5.4 → (2)
multiply (2 ) by 10
0.5n + d = 54 → (3)
subtract (3) from (1) to eliminate d
0.5n = 27 ( divide both sides by 0.5 )
n = [tex]\frac{27}{0.5}[/tex] = 54
substitute n = 54 in (1)
54 + d = 81 ( subtract 54 from both sides )
d = 27
Mary has 54 nickels and 27 dimes
