You may also like

problem icon

Ball Bearings

If a is the radius of the axle, b the radius of each ball-bearing, and c the radius of the hub, why does the number of ball bearings n determine the ratio c/a? Find a formula for c/a in terms of n.

problem icon

Air Routes

Find the distance of the shortest air route at an altitude of 6000 metres between London and Cape Town given the latitudes and longitudes. A simple application of scalar products of vectors.

problem icon


The probability that a passenger books a flight and does not turn up is 0.05. For an aeroplane with 400 seats how many tickets can be sold so that only 1% of flights are over-booked?

Debt Race

Age 16 to 18 Challenge Level:

Note that after the payments on the 1st June 2009 the debts will be

100,000 (1+R) - P

where R is the interest rate and P is the payment.

The interest charged in the second year will be (1+R) lots of this amount