A fête stall's wheel is split into four coloured sectors — red, blue, green and yellow. The red sector measures 100°, the blue 80° and the green 110°. The wheel is given a hard spin and stops at a random position. What is the probability that the pointer ends on yellow?

The four angles must add to 360°, so yellow takes 360 − (100 + 80 + 110) = 70°. On a wheel with unequal sectors the probability of a colour is its angle out of 360°, giving 70/360 = 7/36. Treating the four sectors as equally likely gives 1/4, which would need every angle to be 90°; 11/36 is the green sector, 110/360; and 7/360 divides only the 7 of '70' by 360.