1. Use a thumbtack to punch a hole in the bottom of each cup. Tack the five cups to the cardboard, one under another.

2. Tape the strip of paper vertically on the glass jar, and put the jar beneath the bottom cup.

3. For a test run, fill the top cup with water and make sure the water drips smoothly through each cup.

4. Now pour out the water from the test run and fill the top cup again. Use a timer and, at the end of every five minutes, mark the water level on the paper taped to the jar.

5. When all the water has dripped into the jar, you’ll be able to use this “clock” to keep track of time.

6. For example, start your water clock again. Use the five-minute marks to time how long it takes you to do your homework, practice playing an instrument, or setting the table.