Match the units, then cut it down

A packet holds 500 g of rice. A bag holds 2 kg. What is the ratio?

The rule

The ratio is 1 : 4.

Match the units first. For example, 1 kg is 1000 g. Then divide both parts by the highest number that divides both.

A ratio is in simplest form when only 1 divides both parts.

• 12 and 18 both divide by 6. 12 ÷ 6 = 2 and 18 ÷ 6 = 3. That gives 2 : 3.
• 90 and 150 both divide by 30. 90 ÷ 30 = 3 and 150 ÷ 30 = 5. That gives 3 : 5.
• 450 mL and 600 mL (millilitres) both divide by 150. That gives 3 : 4.