Math: see how to make the simple rule of three

The procedure is used to solve problems involving directly or inversely proportional quantities

In Enem, questions involving the simple three rule are very common. In general, these are simple problems to solve and which can guarantee you some points in the final average. Then check out how to fix this to boost your rating. I wait!

What is the simple rule of three?

The simple rule of three is a practical process for solving problems with four values ​​of which three are known and we need to determine the fourth. The resolution of this kind of problem it’s very simple. Just set up a table (proportional) and solve an equation. I wait:

quantity types

To solve problems with simple rules of three, you must first understand two more concepts about quantities. Are they:

Directly proportional quantities

Two quantities are directly proportional if, by increasing one of them, the other increases in the same way. proportion from the first.

Example:

A car travels 80 km in 1 hour. Thus, the same vehicle will travel 160 km in 2 hours, or 320 km in 4 hours. Each time the distance traveled by the car increases, the elapsed time increases in direct proportion:

80 km / 1 hour – 160 km / 2 hours – 320 km in 4 hours

inversely proportional quantities

Two quantities are inversely proportional when, by increasing one, the other decreases with the same speed as the first.

Example:

Now our car, driving along a road in good condition, travels 100 km in 1 hour. When crossing a slightly worse road, it takes 2 hours to travel another 50km. On a bad road, the car takes 3 hours to drive 25 km:

1 hour / 100km – 2 hours / 50km – 3 hours / 25km

See it increased the time spent on and reduced the distance traveled. In this case, we have inversely proportional or inversely proportional quantities.

Problem 1:

At a barbecue for 50 people, Fábio bought 30 kilos of meat. If Fábio invited 100 people, how many kilos of meat would he have to buy? Note that this is a proportionally direct problem, as by increasing the number of people invited, Fabio will have to increase the amount of meat.

The calculation is: 100 x 30 ÷ 50 = 60. Paulo will need 60 kilos of meat to be able to grill for 100 people.

Problem 2:

50 men build a council house in 22 hours. How many hours would it take 100 men to build such a house? Note that we have an inverse proportional problem here. Increasing the number of men workingthe time taken to build the house will decrease.

The calculation is: 50 x 22 ÷ 100 = 11. The 100 men would take 11 hours to build.

Edited by Tao Consult

Source: Terra

Rose

Rose James is a Gossipify movie and series reviewer known for her in-depth analysis and unique perspective on the latest releases. With a background in film studies, she provides engaging and informative reviews, and keeps readers up to date with industry trends and emerging talents.