Lidl supermarket said it had record UK sales in December, with a rise of 16% on the same period in 2016.
Customers bought about #### tonnes of Brussels sprouts.
I told my class this and said that the first digit of the number of tonnes of sprouts was a 6. They then worked out a likely number.
What they did is below.
.
.
.
.
.
.
.
.
.
.
.
.
Here is one solution. Others were shared too.
- Assumption: 1 sprout weighs about 10g. We know that 1 tonne = 1 million g, so this is 1/100,000 of a tonne.
- Assumption: Each person in the country has 5 sprouts at Christmas.
- Assumption: There are 64 million people in the country.
Multiplying these gives a total sale of 3200 tonnes of sprouts.
Some people buy these from supermarkets (and there are lots of these: Tesco, Sainsburys, Morrisons, Asda, Waitrose, Lidl, Aldi, M&S, Co-Op, Spar), some from local shops and others will grow their own.
Those studying business studies predicted that Lidl might have approx 10% market-share.
We assumed that this meant they sold 10% of the sprouts too (this is an assumption we need to make. For example, Iceland (the shop) has more frozen food, so their market share couldn't be used to predict sales for fresh produce).
Lidl would therefore sell 320 tonnes of sprouts.
The next part is the thing I found particularly interesting. The students pointed out that 320 tonnes was almost exactly midway between 60 tonnes and 600 tonnes. The halfway point is 330 tonnes. The students were aware that in an answer as full of estimates as this they couldn't say that their 320 is less than 330 (which is right and sensible), but they were unclear whether they should round up to 600 or round down to 60.
After discussion they were happy with the idea that we usually think in a multiplicative way about our errors in a question like this (so we predicted 5 sprouts per person, but it could have easily been double that). To get to 600 you multiply by a number less than 2, whereas if you divide by 5 you haven't reached 60. They decided on 600 tonnes as the answer.
Here is the start of the story (from the BBC News site):
After discussion they were happy with the idea that we usually think in a multiplicative way about our errors in a question like this (so we predicted 5 sprouts per person, but it could have easily been double that). To get to 600 you multiply by a number less than 2, whereas if you divide by 5 you haven't reached 60. They decided on 600 tonnes as the answer.
Here is the start of the story (from the BBC News site):
Lidl supermarket said it had record UK sales in December, with a rise of 16% on the same period in 2016.
Customers bought about 600 tonnes of Brussels sprouts
