Important Formulae

Conversion method from $km/h$ to $m/s$

Divide the speed value by $3.6$ (or multiply by $\frac{5}{18}$)

Average speed formula

$$v_{\text{avg}} = \frac{\text{total distance}}{\text{total time}}$$

The smaller angle between the hour and minute hands

Difference between $\left(30H+0.5M\right)$ and $6M$

Permutation formula for selecting $r$ items from $n$ distinct items (order matters)

$$P(n, r) = \frac{n!}{(n - r)!}$$

Combination formula for selecting $r$ items from $n$ distinct items (order does not matter)

$$C(n, r) = \binom{n}{r} = \frac{n!}{r!\,(n - r)!}$$