Algebra story problems

[calnelly]

1) Doug had a pile of quarters and nickels. He had three times as many nickels as quarters. If the pile of coins was worth two dollars and eighty cents, how many quarters does he have.

Your help is greatly appreciated.

 

[stapel]

If he has three times as many nickels as quarters, then you can make groups of one quarter and three nickels. What is the value of a group?

How many of these groups does it take to add up to $2.80?

So how many quarters does he have?

Eliz.

 

[calnelly]

The trouble is writing that out in an equation.

 

[Denis]

The trouble is writing that out in an equation.

WHY is that trouble?
.25 times the number of quarters + .05 times the number of nickels = 2.80;
number of nickels = 3 times the number of quarters:
if you can't handle that, you need classroom help...

 

[calnelly]

never mind I got it on my own a while ago.
3q+q=280
25q+3q=280
28q = 280
---- -----
28 28

q=10 quarters

10 times 25 equals 250 cents plus 10 times 3 which equals 280!

Oh yeah and give a 6th grader a break.

 

[stapel]

The trouble is writing that out in an equation.

Perhaps next time, you might want to include those instructions, since otherwise we have no way of knowing.

Thank you.

Eliz.

 

[Mrspi]

Ummmm......
I don't really understand what you DID there to get q = 10.

But....I think you'd better re-check your answer.

There are supposed to be three times as many nickels as quarters. If there are 10 quarters, there would be 30 nickels. And I don't think that 10 quarters and 30 nickels add up to $2.80!!

Let q = number of quarters
then 3q = number of nickels

.25q is the value of the quarters
.05(3q) is the value of the nickels

.25q + .05(3q) = 2.80
.25q + .15q = 2.80
.40q = 2.80
q = 7

So, there are 7 quarters, and 3q, or 21 nickels.

7 quarters are worth .25(7) or $1.75
21 nickels are worth .05(21) or $1.05
$1.75 + $1.05 = $2.80