Keisha has a collection of dimes and nickels worth a total of $4. If she has 50 coins in all, how many nickels does Keisha have?

30 dimes+20 nickels

30x10=300

20x5=100

total 400 cents = $4

Nickels (n) : $0.05

Dimes (d) : $0.10

Set up a system of equations

Cost/Worth:.05n +.10d = 4.00

Quantity: n + d = 50

Use elimination or substitution to solve.

I am using the elimination method:

100 (.05n +.10d = 4.00) → 5n + 10d = 400

-10 (n + d = 50) → - 10n - 10d = - 500

-5n = - 100

n = 20

Plug that into one of the original equations to solve for "d"

n + d = 50

(20) + d = 50

d = 30

Answer: there are 20 nickels and 30 dimes.