a The radius of the Earth is found to be 6.4 x 10m correct to two significant figures. Find the upper bound on the possible value of the radius. b Hence find the upper bound on the surface area of the Earth, modelling it as a perfect sphere. c A textbook states that the area of the Earth is 5.10 x 10^m'. Find the percentage error if the upper bound found in part b had been used as an estimate A right pyramid has a square base with sides of length 4 cm. It has a height of 6cm. a Find the volume of the pyramid. b Find the acute angle between the sloping edge of the pyramid and the base.