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Help me write the process A job, a alone to do 4 hours to complete, B alone to complete 6 hours, how many hours to complete their cooperation requirements writing process
Set the total amount of work as 1
The efficiency of a is 1 / 4, and that of B is 1 / 6
So it takes time: 1 / (1 / 4 + 1 / 6) = 2.4 hours
If X-12 + X + y-25 + Z & sup2; - 10z + 25 = 0, the triangle with X, y, Z as three sides is () triangle
z²-10z+25=(z-5)²
The left three terms of the equal sign are all nonnegative. If the equation holds, all three terms are 0
That is, x = 12, x + y = 25, z = 5
So we have x = 12, y = 13, z = 5
Obviously, Z & # 178; + X & # 178; = y & # 178;
So according to the Pythagorean theorem, the answer is a right triangle
I wish you progress in your study~~~~
In the orchard, there are 84 more peach trees than pear trees. The number of peach trees is three times that of pear trees. How many are the two kinds of trees?
There are 84 more peach trees than pear trees in the orchard. Peach trees are three times as many as pear trees. That is to say, peach trees are two times as many as pear trees, and these two times are 84. Therefore, pear trees are 84 / (3-1) = 42 and peach trees are 42 * 3 = 126
It takes 9 minutes for a 2-meter-long wood to be sawn into a 0.5-meter-long segment. How many minutes does it take for a wood to be sawn into a 0.2-meter-long segment?
2 / 0.5 = 4, that is to say, a 2-meter-long saw can be cut into 4 sections of 0.5 meters, that is, it needs to be sawed three times, so the time required for each time is 9 / 3 = 3 minutes
2 / 0.2 = 10, it can be sawed into 10 sections of 0.2m, that is, it needs to be sawed 9 times, t = 9 * 3 = 27 minutes
It takes 27 minutes
It has a three digit number. It consists of 1, 3 and a number
If 1 is replaced by 3 and 3 by 4, the other number remains unchanged
Get half of the new number 9 larger than the original number
Let that number be X
And then suppose it's in the hundreds and the tens
And then 100 is 100x + 10 + 3
Or 100x + 30 + 1
Then you change the number, subtract it, you try more times, and the result will come out
12 cattle can eat all the forage of 0.1 hectare pasture in 28 days, 21 cattle can eat all the forage of 0.3 hectare pasture in 63 days. How many cattle can eat all the forage of 0.72 hectare pasture in 126 days? (the amount of original forage in each hectare pasture is equal, the amount of grass growth in each hectare pasture is the same, and the amount of grass eaten by each cattle is the same.)
Suppose x cattle can eat all the forage of 0.72 hectare pasture in 126 days, the original forage amount per hectare pasture is a, the daily forage growth amount per hectare pasture is B, and the daily forage amount per cattle is C
12*28c=0.1a+0.1*28b
21*63c=0.3a+0.3*63b
The solution is: B = 30C, a = 2520c
x*126c=0.72a+0.72*126b
The solution is x = 36
A: 36 cattle can eat all the pasture of 0.72 hectare in 126 days
There are 1360kg apples, oranges and bananas in the fruit shop. Three fifths of the apples and 70kg bananas are sold. After the oranges increase by 25%, the weight of the three kinds of fruits is equal. How many kg of the three kinds of fruits are they originally?
It's better not to use quadratic equations
Let's suppose there are x kg apples, y kg oranges and Z kg bananas
X+Y+Z=1360
(1-3/5)*X=Z-70
Z-70=(1+25%)Y
We can get x = 750 kg (Apple), y = 240 kg (Orange) and z = 370 kg (banana)
Teach math problems and explain the truth
A and B start from ab at the same time, meet 10 kilometers away from the midpoint and continue to move forward. 2 / 3 hours later, a arrives at B, and B still has 1 / 3 of the whole journey. How many kilometers is the distance between AB and B
Let AB distance be a, and it takes a total of 5 / 3 hours for a to complete the whole journey. Let a speed be x, then a = 5 / 3 * X
And a / 2 + 10 = 1 * x --- > A + 20 = 2x
By subtracting the above two equations, we can get: X / 3 = 20 --- > x = 60 --- > A = 100 (km)
A math problem, but requires formula (online)
If a packet of sugar is given to 12 people, the difference is 2 pieces. If it is given to 15 people, the remaining 13 pieces, how many pieces does this packet of sugar have at least?
Sum is to make an equation or formula
If you add two pieces to this packet of sugar
It can be divided equally by 12 people and 15 people
The least common multiple of 12 and 15 is 60
This packet of sugar is at least 60-2 = 58
60n-2, (n is a positive integer)
When n = 1, the minimum value is 58
The number of literature and art books is twice that of science and technology books. Story books are 82 less than the total number of literature and art books and science and technology books. There are 300 science and technology books. How many story books are there
The number of literature and art books is twice that of science and technology books. There are 300 science and technology books, and the number of literature and art books is 300 * 2 = 600,
The total number of story books is 82 less than literature books and science and technology books, and the number of story books is 600 + 300-82 = 818
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