Divide 100 people into four teams. The number of the second team is 3 / 4 of the number of the first team, and the number of the third team is 4 / 5 of the number of the first team. How many people are there in the fourth team?

Divide 100 people into four teams. The number of the second team is 3 / 4 of the number of the first team, and the number of the third team is 4 / 5 of the number of the first team. How many people are there in the fourth team?

There are X members in the first team and y members in the fourth team
X+3/4X+4/5X+Y=100
Let's solve this Diophantine equation,
10. Y is a positive integer, so x is a common multiple of 4,5. Here we can only take 20,
So the fourth team has 100-20-15-16 = 49
They are 20 people in the first team, 15 people in the second team, 16 people in the third team and 49 people in the fourth team

There are two engineering teams. The first team has 120 people. If 20% of the number of the first team is transferred to the second team, then two-thirds of the number of the second team is exactly three-quarters of the number of the first team. How many people are fewer in the second team than in the first team

120 × 20% = 24, 20% of the first team is 24
120-24 = 96, now the number of the first team
96 × 3 / 4 △ 2 / 3 = 108 people, the number of the second team now
108-24 = 84 the number of the original second team
The original second team is less than the first team: 120-84 = 36 people

There are 78 people in the first team and 82 people in the second team. To make the number of people in the first team three times that of the second team, how many people should be transferred from the second team to the first team

The total number remained unchanged
Now the number of the second team: (78 + 82) / (1 + 3) = 40
Adjusted: 82-40 = 42

There are two transport teams, the first team has 36 people and the second team has 24 people. If we want to make the number of the first team twice that of the second team, how many people need to be transferred from the second team to the first team?
The solution is 36 + x = 2 (24-x)
Why is it 2 (24-x) to double the number of the first team to the number of the second team

To solve a problem with an equation, the left and right sides must be equal; to make the second team equal to the first team, the second team must be doubled
To double the number of the first team to the number of the second team, it will be 2 (24-x)