A community hall is in the shape of a cuboid. The hall is 20m long, 15m wide and
4m high.
The community hall needs re-decorating
with new paint for the walls and ceiling,
and new tiles on the floor.
A 20 litre tin of paint covers 40 m2 and costs £15.
1 m2 floor tiles cost £3 each.
Work out the total cost of paint and tiles needed
to re-decorate the community hall.

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters