[The narrator reads out the onscreen text.]

NARRATOR: Question six. Jade buys a 500 gram bag of beads at a market. Each bead has a mass of 0.48 grams. Which of these is the best estimate for the number of beads in the bag: A - 100, B - 250, C - 1000, D - 2500?

It will be easier to estimate the number of beads if we first round the mass of each bead correct to one decimal place. 0.48 is between 0.4 and 0.5. 0.45 is halfway between 0.4 and 0.5. And we know that 0.48 is greater than 0.45, so therefore it must be closer to 0.5 than 0.4. So 0.48 is approximately equal to 0.5. We will approximate the mass of each bead to 0.5 grams. There is 500 grams of beads in the bag, so we can approximate the number of beads in the bag by working out how many lots of 0.5 there are in 500. We know that there are 500 lots of 1 in 500, so there must be twice as many lots of 0.5 in 500, ie, 500 divided by 0.5 is equal to 1000. Therefore C is the best approximation, and the correct answer to the question.

Alternatively, we could work backwards using the options given. Considering Option A. If there were around 100 beads in the bag, each bead would weigh approximately 500 divided by 100, so around 5 grams. This is not close to 0.48 grams. In Option B, we could work out that each bead should weigh 500 divided by 250, which means they would each weigh approximately 2 grams. This is also not close to 0.48 grams. If we continue for each option, we see that the best approximation is indeed Option C.