Equivalent fractions and multiplying by a whole number

When the numerator and the denominator are the same, every part of the whole is counted, so the fraction is exactly one whole: 6/6 = 1, 4/4 = 1 and 10/10 = 1. Whole numbers can be written as fractions too. Each whole is made of as many pieces as the denominator says. If each whole is cut into 4 equal parts, 3 wholes are 3 × 4 = 12 fourths, so 3 = 12/4. The identity property says that adding 0 does not change a number: 3/8 + 0 = 3/8. Multiplying by 1 does not change a number either: 1 × 5/6 = 5/6, which means one group of 5/6. A fraction such as 4/4 is useful because adding it just adds one whole.