posted by Stone .
Kathy has ribbons that have lengths of 7 inches, 10 inches, and 12 inches. Explain how she can use these ribbons to measure a length of 15 inches.
Place the 7-inch ribbon on the 10-inch ribbon. There will be 3 inches left over. Now put the 12-inch ribbon at the end of the 3-inch piece. Voila! You have 15 inches.