Question

Sanjeet paid $32.85 for a file and 3 identical pens.Leon paid $83.50 for 2 such files and 8 such pens.Find the cost of 1 pen.How do you do it?Help pls.

Answer 1

Explanation:

Let f and p represent the costs of a file and a pen, respectively. The two purchases are ...

f +3p = 32.85

2f +8p = 83.50

Subtracting twice the first equation from the second gives an equation for the cost of pens:

(2f +8p) -2(f +3p) = (83.50) -2(32.85)

2p = 17.80 . . . . simplify

p = 8.90 . . . . . . divide by 2

The cost of one pen is $8.90.

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Comment on "how do you do it?"

You are given two purchases related to the costs of two items. Write equations that describe the purchases. (The total cost is sum of the costs of each of the items, which will be the product of the number of items and the cost of each. You have been shopping, so you know this.)

Once you have a "system of equations", there are many ways they can be solved. You are usually instructed on "elimination" and "substitution" as methods of solution. Above, we used "elimination" to eliminate the "f" variable and give an equation only in "p".