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Finding the Reciprocal of a Fraction

(KS2, Year 5)

To find the reciprocal of a fraction, turn the fraction upside down. The reciprocal of 2 over 3 is 3 over 2

Make the numerator the denominator, and the denominator the numerator.

How to Find the Reciprocal of a Fraction

Question

What is the reciprocal of the fraction below? three fifths

Step-by-Step:

1

Make the numerator of the fraction the denominator of the reciprocal. In our example, the numerator of the fraction is 3. $The numerator of the fraction (3) becomes the denominator of the reciprocal$

2

Make the denominator of the fraction the numerator of the reciprocal. In our example, the denominator of the fraction is 5. $The denominator of the fraction (5) becomes the numerator of the reciprocal$

Answer:

We have found the reciprocal of the fraction: five thirds

Finding the Reciprocal of a Mixed Fraction

The method above can be used to find the reciprocal of proper and improper fractions, but can not immediately be applied to mixed fractions. Mixed fractions must first be converted to improper fractions before the method can be applied.

Question

What is the reciprocal of the mixed fraction below? three and two thirds

Step-by-Step:

Add a preliminary step.

0

Convert the mixed fraction to an improper fraction. Three and two thirds equals eleven thirds

The method then continues as before.

1

Make the numerator of the fraction the denominator of the reciprocal. In our example, the numerator of the fraction is 11. $The numerator of the fraction (11) becomes the denominator of the fraction$

2

Make the denominator of the fraction the numerator of the reciprocal. In our example, the denominator of the fraction is 3. $The denominator of the fraction (3) becomes the denominator of the fraction$

Answer:

We have found the reciprocal of the fraction: three elevenths

Lesson Slides

The slider below shows another real example of how to find the reciprocal of a fraction.

What Is a Reciprocal?

The reciprocal of a quantity is the result of dividing 1 by that quantity. Reciprocal of 5 is 1 over 5

Why Is Finding the Reciprocal of a Fraction Useful?

The reciprocal of a fraction is useful for:

the laws of exponents. For example, when the base is a fraction and the exponent is negative. This is equivalent to replacing the fraction with its reciprocal and using the positive exponent.
dividing by a fraction. Dividing by a fraction is equivalent to multiplying by its reciprocal.