To find out how many days your birdseed will last, you can divide the total amount of birdseed by the amount used each day.
You have 3 cups of birdseed and you use \( \frac{2}{5} \) cup per day.
First, convert 3 cups into a fraction: \[ 3 = \frac{3}{1} \]
Next, divide the total birdseed by the daily usage: \[ \text{Days} = \frac{\text{Total birdseed}}{\text{Daily usage}} = \frac{3}{\frac{2}{5}} \]
To divide by a fraction, multiply by its reciprocal: \[ \frac{3}{\frac{2}{5}} = 3 \times \frac{5}{2} = \frac{3 \times 5}{2} = \frac{15}{2} \]
Now convert \( \frac{15}{2} \) to a mixed number: \[ \frac{15}{2} = 7 \frac{1}{2} \]
So, your birdseed will last for 7 and a half days.
If you need the whole number of full days, it will last for 7 full days, and you will have some leftover birdseed for half a day.