Primary 5 Fractions

Keywords

Proper fraction: A fraction smaller than one whole; its numerator is less than its denominator.
Improper fraction: A fraction equal to or greater than one whole; its numerator is at least its denominator.
Mixed number: A whole number together with a proper fraction.
Common denominator: A shared denominator that makes fraction parts the same size.
Simplest form: A fraction whose numerator and denominator have no common factor greater than 1.

Express fractions as decimals

Make tenths, hundredths or thousandths when possible, then write the same amount in decimal form. You can also divide the numerator by the denominator using long division. A mixed or improper fraction may have a whole-number part.

Change a fraction to a decimal

34 = ?

Step 0 of 2

See worked example

Express 78 as a decimal.

Multiply both parts by 125: 7 × 125 = 875 and 8 × 125 = 1000, so 78 = 8751000.
Write 875 thousandths as 0.875.

Answer: 0.875.

Try together

Express 1120 as a decimal.

Reveal the answer

11 × 5 = 55 and 20 × 5 = 100, so 1120 = 55100 = 0.55.

Add and subtract mixed numbers

Give the fraction parts a common denominator. Add or subtract the whole parts and fraction parts; regroup one whole when there are too few fraction parts to subtract.

Choose addition or subtraction

213 + 116 = ?

Step 0 of 4

See worked example

Work out 414 − 123.

Make twelfths: 1 × 3 = 3 and 4 × 3 = 12, so 14 = 312. Also, 2 × 4 = 8 and 3 × 4 = 12, so 23 = 812.
Rewrite and regroup: 414 − 123 = 4312 − 1812, and 4312 = 31512.
Subtract: 31512 − 1812 = 2712.

Answer: 2712.

Try together

Work out 134 + 218.

Reveal the answer

3 × 2 = 6 and 4 × 2 = 8, so 134 + 218 = 168 + 218 = 378.

Multiply fractions

For two fractions, multiply the numerators and multiply the denominators. Treat a whole number as a fraction over 1. Change a mixed number to an improper fraction before multiplying.

Choose the type of multiplication

34 × 8 = ?

Step 0 of 2

See worked example

Work out 23 × 34.

Multiply the numerators: 2 × 3 = 6. Multiply the denominators: 3 × 4 = 12.
Simplify by dividing both parts by 6: 6 ÷ 6 = 1 and 12 ÷ 6 = 2, so 612 = 12.

Answer: 12.

Try together

Work out 214 × 4.

Reveal the answer

214 = 94. Multiply 9 × 4 = 36, then divide 36 ÷ 4 = 9.