. Eric has ⁹∕₁₅ pound of birdseed to put into his feeders. If he puts ¹∕₅ pound in each feeder, how many feeders can he fill?

3 feeders

To find out how many feeders Eric can fill you first need to give 9/15 and 1/5 the same denominators. To do this, find what is called the LCD - lowest common denominator because what the question is asking is how many times can you add 1/5 until it becomes equal to 9/15.

To find the LCD, list out some multiples of 5 and 15. Then find the smallest multiple they both share.

5 - 5 10 15 20 25 30
15 - 15 30 45 60

You can see the smallest multiple 5 and 15 have in common is 15. This means you want to have it so both denominators are 15.

9/15s denominator is already 15 so you don’t need to do anything to this fraction

1/5s denominator is 5. To change the denominator to 15, ask what multiplied by 5 equals 15.
5 x 3 = 15, so multiply both the numerator and denominator by 3 to get an equivalent fraction.

1 x 3 = 3
5 x 3 = 15

1/5 = 3/15

1/5 = 3/15, so Eric is putting 3/15 pound of birdseed into each feeder. He only has 9/15 pound of birdseed in total. 9/15 - 3/15 = 6/15 so after filling 1 feeder he has 6/15 pound of birdseed left. 6/15 - 3/15 = 3/15 so after filling two feeders he has 3/15 pound of birdseed left. 3/15 - 3/15 = 0 so after filling 3 feeders he is out of birdseed.

With 9/15 pounds birdseed Eric can fill 3 feeders.

Main idea on left, details on right