Posted by **Mary** on Tuesday, September 9, 2008 at 7:02pm.

A collection of 30 coins worth $5.50 consists of nickels, dimes, and quarters. There are twice as many dimes as nickels. How many quarters are there?

- Math -
**Reiny**, Tuesday, September 9, 2008 at 7:22pm
Let the number of nickels be N

let the number of dimes be D, so D = 2N

let the number of quarters be Q

but Q would then be 30-N-D

= 30 - N - 2N

= 30 - 3N

now form an equation using the "value" of those coins:

5(N) + 10(2N) + 25(30-3N) = 550

solve for N, then backsubstitute for the others.

Let me know what you got.

- Math -
**Mary**, Tuesday, September 9, 2008 at 7:57pm
so i did...

5n+10(2n)+750-75n=550

5n+20n-75n=-200

-50n=-200

n=4

four nickels

eight dimes

12 quarters

.. thats not right! D:

- Math -
**Mary**, Tuesday, September 9, 2008 at 8:24pm
ohh!

for some reason i multiplied 4 and three to get 12 quarters..

wow silly mistake!

thanks so much for the help!!

- Math -
**Ray**, Tuesday, September 28, 2010 at 11:00am
fuch et just guess

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