In maths we started answering the following
question:
1a: We are buying a boiler for our new school, we have
a choice of two.
A normal boiler costs £100,000
A combined heat and power boiler (CHP) costs £150,000
Which should we buy?
1b: Fuel for the normal boiler will cost £2000
per month.
The CHP boiler will save 2/3 of the bill.
How long will it be before the CHP boiler is cheaper?
1c: You have to borrow the difference in cost between
the two boilers and the interest rate is 5%. How long
will it now be before the CHP boiler is cheaper?
1d: If the normal boiler is serviced twice per year
and the CHP boiler is serviced once per year how long
will it be before the CHP boiler is cheaper if servicing
of both boilers is £500.
What is your final recommendation to the Headteacher
about the boiler for the new school?
Commentary for teachers
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