Each carton holds 23/8 kg of flour. Mei Ling buys 6 such cartons. Find the total mass of flour she buys. Give your answer as a mixed number.
The total mass is 141/4 kg.
Ans: 14{1|4}
How to solve it
Make the mixed number one fraction: 2 times 8 plus 3 is 19, so one carton holds 19 over 8 kilograms.
Multiply by 6 cartons: 6 times 19 is 114. The denominator stays 8, because every part is still one eighth.
Turn it back into a mixed number: 114 is 8 times 14 plus 2, so 114 over 8 is 14 and two eighths.
Simplify the fraction: divide the numerator and denominator of two eighths by 2 to get one quarter.
The total mass is 14 and one quarter kilograms.
The mass in one carton is one number: 19 over 8. Multiply that one fraction by 6 for all six cartons. Write the total as a mixed number, then simplify its fraction.
Practice questions with worked solutions
Question 1 is free to try. The other 6 open in the free trial, each with its full working.
What is the method for multiplying mixed numbers by whole numbers in P5?
This page covers one outcome from the Primary 5 Fractions strand: multiplying a mixed number and a whole number.
What your child learns here
This page covers one outcome from the Primary 5 Fractions strand: multiplying a mixed number and a whole number. The questions are set as equal packets, containers or lengths, so the total is usually a mixed number.
Change the mixed number to an improper fraction before multiplying.
Multiply the numerator by the whole number; the denominator stays the same.
Change an improper answer back to a mixed number and simplify the fraction part.
Another valid way is to multiply the whole-number part and the fraction part separately, then add the two results.
When the fraction parts add up to whole numbers, the answer can be a whole number.
Does the answer make sense?
When the question asks for the total of several equal packets, planks or ribbons, your child's answer must lie between the whole-number part times the count and the next whole number times the count. Four bags of 3 3/8 kg must weigh between 12 kg and 16 kg.
How to practise these questions
Basic questions train multiplying a mixed number by a whole number in everyday totals of mass, capacity and length, and writing the answer in simplest form. Intermediate questions add totals that come out as whole numbers and fraction parts in tenths. Challenge questions go a step further, using part of the total or adding two different products together. Should the fraction part go astray, watch the solution film for that question and redo it later from Revision.
Questions parents ask
Is multiplying a mixed number by a whole number in the Primary 5 syllabus? Yes. The Primary 5 Fractions strand lists multiplying a mixed number and a whole number as one of its outcomes.
Does my child have to change the mixed number to an improper fraction? It is the method the lesson on this page uses, and it works every time. Splitting into the whole part and the fraction part is also correct, as long as both parts are multiplied.
Should the answer be a mixed number or an improper fraction? Write the answer the way the question asks. When it does not say, a mixed number with the fraction in simplest form is the usual way to finish.
