.
Use the proportion
= ,
where x is the unknown mass ("how many tons") under the question.
The proportion expresses very simple idea that the "rate of work" of each truck is the same, measured in tons per truck per day.
From the proportion, find x = = 12*7*3 = 252 tons. ANSWER
By doing in this way, you have easy way to create an equation (a proportion) based on clear idea of the rate of work.
So, you will never make a mistake using this method.
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To see many other similar solved problems, look into the lesson
- Rate of work problems
in this site.
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Surely, with the given "nice numbers" you can solve the problem in other way, too.
If 5 trucks transport 120 tons in 2 days, then it is clear than 1 truck transports = = 12 tons per day.
Therefore, you need simply multiply these 12 tons by 7 and 3 to get the answer 12*3*7 = 252 tons.
But not always you will be so fortunate to have such nice round numbers - and then recall about my major method !