Unit 7 Subtraction of Common Fractions Basic Principles

Unit 7 Subtraction of Common Fractions

Basic Principles of Subtraction of Common Fractions • Subtraction of common fractions follows the same principles as addition of common fractions. – If the denominators are the same, the numerators are subtracted, and the difference is put over the common denominator.

Basic Principles of Subtraction of Common Fractions – If the denominators are not the same, the fractions must be converted to fractions with a lowest common denominator before the numerators can be subtracted. – The fractional difference must then be reduced to lowest terms.

Basic Principles of Subtraction of Common Fractions • Example: – Line up the fractions: – Find a common denominator, then subtract.

Subtraction of Common Fractions • When mixed numbers are subtracted, the fractional part of each mixed number must first be converted to the lowest common denominator. – If the numerator of the fraction in the subtrahend (number to be subtracted) is larger than the numerator of the fraction in the minuend (number from which it is to be subtracted), one unit must be borrowed from the whole number in the minuend.

Subtraction of Common Fractions • Example: – Line up the problem: – Find a common denominator: – Subtract (borrow):

Practical Problem • A pediatric nurse measures 1 -year-old Nicky and finds that he is 37 1/4 inches (") tall. At birth, Nicky was 18 3/4" tall. • How much did Nicky grow in 1 year?

Practical Problem • Line up the fractions and subtract: • Jenny grew .