Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

August 11, 2014

When my boys were toddlers, it seemed like no matter how many fancy xylophones or wooden drums I bought them, they always seemed to gravitate towards our kitchen pantry with all its pots and pans. The neighbors must have cast a dirty look or two towards our house when my little rock musicians started banging on those makeshift drums with their wooden spoons!

To preserve my ears and my sanity, as soon as they were old enough to understand the phrase “tap gently”, I let them make music with water glasses. They were amazed to hear the range of notes they could produce just by tapping glasses with a spoon! And once they realized that hitting the glass too hard would actually make the sound stop (i.e. the glass would break), they were more than happy to use their indoor hands and voices. They loved their new musical instrument, and the absence of all that metallic clanging was certainly music to my ears.

## Make a Musical Water Glass Scale

You’ll need:

• 8 identical water glasses
• 1 plastic spoon
• 1 pitcher of water
• 1 set of measuring cups

Arrange the water glasses in a line and fill them up with varying amounts of water. Try to make the increments of water equal. For example, start with 1/8 cup of water in the first one, then fill each succeeding glass so that it has 1/8 cup of water more than the previous glass in line. Tap each glass with the plastic spoon and enjoy the sounds they make!

Experiment by changing the amount of water in each glass and hearing how the sounds change.

How to Play Mary Had a Little Lamb

At some point, your little one is going to tire of playing scales or random notes and move on to playing an actual tune. There’s nothing simpler than everyone’s first nursery rhyme, the 3-note Mary Had a Little Lamb. Here’s how to play it with water glasses:

You’ll need:

• 3 identical large glass tumblers or mason jars
• 1 plastic spoon
• 1 set of measuring cups
• Water (How much water in total will you need?  Ask your school-aged child to add up the fractions below! Then ask your preschooler to measure it out.)
• Masking tape and a pen for labeling

Arrange the tumblers in a line and fill them up with the following amounts of water:

Tumbler 1: 1 3/4 cups

Tumbler 2: 1 1/2 cups

Tumbler 3: 1 1/4 cups

Label the tumblers 1, 2, and 3.  Tap the glasses in the following order:

3-2-1-2-3-3-3

2-2-2

3-3-3

3-2-1-2-3-3-3

3-2-2-3-2-1

### Fun Fact

Each glass makes a sound when you tap its side with a spoon (to avoid breakage, use a plastic spoon, not a wooden or a metal one) because the spoon causes a vibrating sound wave. The sound wave travels through the water in the glass and eventually reaches your ear. Each glass makes a different sound because the sound waves travel through the water at different speeds, causing vibrations at different frequencies. (Frequency refers to the number of times a sound wave vibrates per second).

The glasses with the most water produce the lowest sounds because the sound waves travel slowest (causing the lowest frequency vibrations) through all that water. The glasses with the least amount of water produce the highest sounds because sound waves travel fastest (causing the highest frequency vibrations). In fact, when the sound waves of one note vibrate at twice the frequency of another, the two notes are exactly one octave apart!

Feeling inspired by the lovely tones of your musical glasses? Check out this Bedtime Math problem, but beware: it may lead to a more involved musical project.