## Time and Distance

### important fomulae

Speed= $$\left(\frac{\text { Distance }}{\text { Time }}\right)$$

Time =$$\left(\frac{\text { Distance }}{\text { Speed }}\right)$$

Distance = (Speed x Time).

### Conversions :

conversion of km/hr to m/sec

$$\mathrm{km} / \mathrm{hr}=\left(x \times \frac{5}{18}\right) \mathrm{m} / \mathrm{sec}$$

conversion of m /sex to km/hr

x  $$\mathrm{m} / \mathrm{sec}=\left(x \times \frac{18}{5}\right) \mathrm{km} / \mathrm{hr}$$.

### remember points

1. If the ratio of the speeds of A and B is a : b, then the ratio of the times taken by then to cover the same distance is   $$\frac{1}{a}: \frac{1}{b}$$ or b: a.
2. Suppose a man covers a certain distance at x $$\frac {km}{hr}$$ and an equal distance at y km /hr . Then the average speed during the whole journey is $$\left(\frac{2 x y}{x+y}\right) \mathrm{km} / \mathrm{hr}$$.