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This content is taken from the National STEM Learning Centre's online course, Maths Subject Knowledge: Fractions, Decimals, and Percentages. Join the course to learn more.
5.3

## National STEM Learning Centre

Skip to 0 minutes and 7 seconds PAULA KELLY: OK, so some of our divisions aren’t always going to give us a whole number answer, OK? So we’re looking at 99 divided by 12. As you did earlier, I’ve got my 12 times table to help me. So we do 99 divided by 12. I can see from here that eight lots of 12 are 96. Nine lots of 12 is 108. That’s too big, OK. So if we start with our 8 times 12, and I can see from here, I get 96. Our target number is 99, so our difference is 3, so not in our 12 times table.

Skip to 0 minutes and 47 seconds MICHAEL ANDERSON: No.

Skip to 0 minutes and 48 seconds PAULA KELLY: So we’re going to write, actually– 99, if we divide it by 12, gives us 8 whole ones. Sometimes at primary, students are quite happy to write 8 remainder 3, or the small r of three. Mathematically, we can be more accurate, though. We could write this as we’ve got 8 whole ones. 3 is our remainder, and we’re dividing by 12, so we’ve got 8 and 3/12. We know from earlier as well, we wouldn’t ever leave a fraction like this. We’d always simplify, so we’ve got 8 whole ones still. 3 is a factor both of these, one 3 in there, and four 3’s in there. So final answer, 8 and 1/4.

Skip to 1 minute and 34 seconds MICHAEL ANDERSON: Brill.

# Dealing with remainders

The division calculations in the previous step divided exactly, leaving a whole number answer. When the numbers do not divide exactly we end up with a remainder.

Consider the calculation $$99 \div 12$$.

You may like to attempt this calculation before proceeding.

In this video Paula and Michael explain what should be done when the answer produces a remainder. In some contexts it makes sense to leave your answer a whole number and a remainder but in most cases it makes more sense to leave your answer as a mixed number.

## Problem worksheet

Complete question 3 from this week’s worksheet.