pecan_tart said:
Problem: 9 pens cost $11 and x cents; 13 pens cost $15 and y cents. Find x and y.
How do I attack this?
Since you're in a pre-pre-algebra course (else you wouldn't have posted this to the "Arithmetic" category), I'm not quite sure how you're supposed to approach this. Are you at all familiar with variables? (Those are the letters, in this case, "x" and "y", that are used in place of numbers.) If not, start here:
. . . . .Google results for "variables"
Once you're comfortable with that concept, let's look at the exercise.
You have nine units costing 11 + x, where 0
< x
< 99. (The "
<" means "less than or equal to". The value of x has to be something between zero and ninety-nine, because that's how "cents" are counted when we've also got "dollars".) Since you've got nine pens, the price must be some multiple of 9. Looking at the price entirely in terms of "cents", the price is 1100 + x and is equal to 9 times... something. What "9 times ... something" values fit between 1100 and 1199? Make a table, listing the multiples of 9, and marking down how much each individual pen would be for each value, and also what "x" would be. For instance, 1107 = 9(123), making each pen cost $1.23 and making x equal to 7.
Now do the same sort of thing for the thirteen pens.
Comparing the tables, you should be able to find a matching per-pen price. Use this to find the values of x and y. :idea:
Have fun!
Eliz.
