word problem: Berni Davis has been saving dimes and quarters

[jshaziza]

Berni Davis has been saving dimes and quarters. He has 94 coins in all. If the total value is $19.30, how many dimes and how many quarters does he have? Could you guys show me the formula I have to use to solve this?

 

[jwpaine]

Hey.

You could set up a system of equations:

94 coins in all
total value = $19.30
dimes and quarters

{.10(D) + 0.25(Q) = $19.30
{D + Q = 94

Solve using substitution method from second equation. (easier)

Hope this helps.

 

[Denis]

{.10(D) + 0.25(Q) = $19.30

Sometimes easier to get rid of decimals; multiply by 100:
10D + 25Q = 1930

Also simplify if possible; divide by 5:
2D + 5Q = 386

Now do the substitution, as jw told you...

 

[jshaziza]

Darn I forgot about the substitution method, I had the elimination method stuck in my mind. Thanks guys.