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

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Answer 1 · 2016-11-15T12:55:26

I got $50s$

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

Answer 2 · 2016-12-03T21:17:00

It will take 50 seconds to run 1000 metres

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 $t$

$20/1-=1000/t$
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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.

$color(green)(20/1color(magenta)(xx1)" "-=" "20/1color(magenta)(xx50/50))color(blue)(" " =" " 1000/50)$

It will take 50 seconds to run 1000 metres