On a clock face each hour division is 360/12=30°.
8 o’clock is therefore 60° from 6 o’clock, the lowest position.
If O is the centre of the wheel, P the lowest point and Q the 8 o’clock position then the perpendicular QN onto OP is such that ON=OQcos60=5/2=2.5in, because OQ=OP=5in. Therefore NP=OP-ON=2.5in and the height of Q from the ground is 2.5+(6.5-5)=4in.