You can put this solution on YOUR website! 90 km/hr * 20 min will have a mismatch in the units of measure.
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20 min / 60 min/hr = 1/3 hr
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90 km/hr * 1/3 hr = 30 km
You can put this solution on YOUR website! In 1 hour.........90km
In 60 minutes.....90km
In 60/3 minutes..90/3 km
In 20 minutes....30 km
Tranin will go 30km in 20 minutes
Alternatively
Speed = 90km/hour
Time = 20 minutes
Distance = Speed * time
Distance = 90/hour * 20minutes
Distance = 90/60 minutes * 20minutes
Distance = 90/60 * 20
Distance = 30/20 * 20
Distance = 30km