Posted by allen on Friday, February 25, 2011 at 7:36pm.
At the school store, 5 pens sell for $1.25. Which proportion will help find the cost of 12 pens?

math  Ms. Sue, Friday, February 25, 2011 at 7:38pm
What are your choices?
What do you think the answer is?

math  allen, Friday, February 25, 2011 at 7:41pm
a. 5/12=1.25/x
b. 5/12=x/1.25
c. 5/x=12/1.25
d. x/5=12/1.25

math  allen, Friday, February 25, 2011 at 7:42pm
I say its c

math  Damon, Friday, February 25, 2011 at 7:51pm
5 pens / 12 pens = 1.25 dollars/x dollars
It helps to write the units, pens and dollars.
so
I claim a is correct
although I myself would have written the same thing as
5 pens/1.25 dollars = 12 pens/x dollars
which comes out the same

math  Anonymous, Friday, February 25, 2011 at 11:11pm
5 pens cost 1.25$
1.25/5=0.25$ Price of one pen
12*0.25=3$ Price of 12 pens
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