Succeed with maths – Part 1
Succeed with maths – Part 1

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Overall cost

You’re nearly there now – just one more step in the next section to finally work out the DIY cost.

Activity 10 The price of doing it yourself

Timing: Allow approximately 10 minutes

Now work out the DIY cost using all the information you’ve gathered and worked out.


  • Each roll costs £15.
  • There is a ‘three-for-two’ special offer.
  • I will also need to buy some safety equipment costing £40.
  • I need to buy 20 rolls of insulation.


Since I need to buy 20 rolls of insulation, I will be able to take advantage of the ‘three-for-two’ offer. So for every three rolls I purchase, I only pay for two rolls.

So cost of three rolls = £15 × 2 = £30

To determine how many times I will get to take advantage of the offer, a picture can be used.

Image of 20 rolls of installation arranged in 2 rows, each containing 10 rolls.
Figure 10 20 rolls of insulation

Since there are six sets of three rolls, it will cost £30 × 6 = £180. Unfortunately, the two additional rolls won’t be on offer, so the insulation will cost £180 + £15 + £15 = £210.

Finally, the safety equipment is £40. This puts the total cost at £210 + £40 = £250

You can now move onto the final step in the problem solving cycle – interpreting the answer

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