To divide an amount in a given ratio, think in units. Add the parts of the ratio to get the total number of units, find what one unit is worth, then multiply for each share. For example, sharing $20 in the ratio 2 : 3 gives 5 units in all, so one unit is $20 ÷ 5 = $4; the shares are $8 and $12. Drawing a bar model of the parts and the whole makes this clear.
Worked example
Problem Share $60 between Ann and Ben in the ratio 2 : 3. How much does each get?
Add the parts to get the total units: 2 + 3 = 5 units.
Find one unit: $60 ÷ 5 = $12.
Multiply for each share: Ann = 2 × $12 = $24; Ben = 3 × $12 = $36.
Tip Check your shares add back to the total: $24 + $36 = $60.