Question

On a stopwatch, the tip of the second hand moves 2 cm in 15 seconds. How long is the second hand?

Answer 1

`4/pi = 1.27 cm`

Explanation:

15 seconds is 1/4 of the circumference of the circle that the second hand moves.

Let the length of the second hand be `r`

Circumference `= 2pir`

`1/4` of the circumference = `1/4*2pir=1/2pir`

`=> 1/2pir=2 cm`
`r=4/pi=1.27 cm`