Answer:
On 5 liters of petroleum he can go 100km.
He needs 37.5 liters of petroleum to go 750km.
Explanation:
He goes 20km on 1 liter. Now we must find how far he can go on 5 liters.
1 * 5 = 5
20 * 5 = 100
The reason we multiplied was because we had to multiply 1 by 5 to get the number of liters of petroleum and what you to one side you must do to the other.
To find how many liters are needed to go 750km you must divide:
750/20 = 37.5
He needs 37.5 liters of petroleum to travel 750km.
Hope this helps! :)