A comparison of two quantities by division. You can write a ratio three different ways.

You can use a ratio to compare part to part. The ratio of black piano keys to white piano keys in the pattern is 5 : 7. You can also compare part to whole. The ratio of black piano keys to all piano keys is 5 : 12.

Write each ratio in three ways. Use the pattern of piano keys shown above. White keys to all keys: Black keys to white keys:

Write the ratio as a decimal. Round to the nearest hundredth when necessary.

Find two ratios equal to ×2 ÷2

Find two ratios equal to ×2 ÷3