# A boy runs at a speed of 20 m/s.How much time will he take to cover a distance of 1 km?

Nov 15, 2016

I got $50 s$

#### Explanation:

1 km corresponds to $1000 m$ so considering that:
$\text{speed"="distance"/"time}$
we can rearrange and get:
$\text{time"="distance"/"speed} = \frac{1000}{20} = 50 s$

Dec 3, 2016

It will take 50 seconds to run 1000 metres

#### Explanation:

Using ratio in the fraction style format

Given:" "("distance")/("time")-> ("metres")/("seconds")->20/1

We need 1 km which is the same as 1000m

Let the unknown time in seconds be $t$

$\frac{20}{1} \equiv \frac{1000}{t}$
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To change 20 into 1000 multiply by 50

If you multiply by 1 you do not change the value. However, 1 can come in many forms.

$\textcolor{g r e e n}{\frac{20}{1} \textcolor{m a \ge n t a}{\times 1} \text{ "-=" "20/1color(magenta)(xx50/50))color(blue)(" " =" } \frac{1000}{50}}$

It will take 50 seconds to run 1000 metres