How long is the minute hand on a clock whose tip travels 15 cm from 1:15 to 1:30 to the nearest tenth?

a. 10.1 cm

b. 9.5 cm

c. 6.0cm

d. 0.2 cm

The answer is:

B: 9.6cm

We are given the data of the minute hand traveling from 1:15 to 1:30 and a displacement of the hand by 15 cm. In this case. the arc length is the 15 cm while the angle of the sector can be derived from the clock times. The angle between 1:15 to 1:30 is approximately 90 degrees or pi/2. hence the radius can be computed from:

s = r theta

15 = r * pi/2

r = 9.55 cm