100 pens cost x dollars. how many pens can be purchased for 50 cents, assuming the same rate?

100 pens cost x dollars.

Therefore 1 pen costs

x/100 dollars/pen

50 cents = 0.5 dollars. It can purchase

(0.5 dollars) / (x/100 dollars/pen)

= 50/x dollars

Answer: 50 cents can purchase 50/x pens