Determine the better buy by comparing unit rates. 1. 20 pens for $1.60 or 25 pens for $2.25 2. 13 berries for $2.60 or 17 berries for $3.06

To find the better buy we have to find the cost per pen for each.

1. 20 pens for $1.60 -> 1.60/20 = .08 cents per pen.
25 pens for $2.25 -> 2.25/25 = .09 cents per pen.

The best buy is 20 pens for $1.60 because it's cheaper per pen. 

2. 13 berries for $2.60 -> 2.60/13 = .20 cents per berry
17 berries for $3.06 -> 3.06/17 = .18 cents per berry

The best buy is 17 berries for $3.06 because it's cheaper per berry.

1. 20 pens for $1.60
2. 17 berries for $3.06