There are 28 boys and 21 girls in class 51. What percentage of the total number are boys? What questions can you ask?

There are 28 boys and 21 girls in class 51. What percentage of the total number are boys? What questions can you ask?

28/（28+21）
How many more boys than girls?
What percentage of the class are girls?
2.5 * (2 / 5-1 / 3) + 2.1
2.5*(2/5-1/3)+2.1=2.5*(6/15-5/15)+2.1=5/2*1/15+2.1=1/6+21/10=5/30+63/30=68/30=34/15
So the cargo is 2.5 ^ (1-4 / 5) = 12.5 tons, so 1 / 4 is transported away, and the remaining 12.5 × (1-1 / 4) = 9.375 tons. Thank you for your adoption. The cargo is 2.5 ^ (4 / 1-5)
There are 21 boys and 15 girls in class 5 of grade 5. The number of boys is several times of that of girls. What is the percentage of girls in boys?
There are 21 boys and 15 girls in class 5 of grade 5. The number of boys is 1.4 times that of girls, and girls account for 5 / 7 of boys
Xiaojun read a book, read 2 / 3 of the book in 7 days, and read 40 pages in the next five days. How many pages does the book have?
2. One fifth of a bag of flour is used, and 20kg is left. How many parts of this bag of flour is left? How many kg does this bag of flour weigh?
Because I have read two thirds of the book in seven days, I have 1-2 / 3 left. Suppose the book has x pages x * (1-2 / 3) = 40 x * (1 / 3) = 40 x = 120, so the book has 120 pages. 2 the remaining flour is 1-1 / 5 = 4 / 5 of the bag of flour. Suppose the weight of the bag of flour is x kg x * (4 / 5) = 20 x = 25, so the weight of the bag of flour is 25 kg
40 / (1-2 / 3) = 120 pages
The rest is 1-1 / 5 = 4 / 5, flour bag 20 / (4 / 5) = 25kg
I read two-thirds of the book in seven days
So there's 1-2 / 3 left
Suppose the book has x pages
The remaining 1-2 / 3 is 50 pages
So x * (1-2 / 3) = 50
x*(1/3)=50
x=50*3=150
So this book has 150 pages
The remaining flour is 1-1 / 5 of this bag of flour = 4 / 5
Suppose this bag of flour weighs x kg
So x * (4 / 5) = 20
x=20*5/4=25
To begin with
I read two-thirds of the book in seven days
So there's 1-2 / 3 left
Suppose the book has x pages
The remaining 1-2 / 3 is 50 pages
So x * (1-2 / 3) = 50
x*(1/3)=50
x=50*3=150
So this book has 150 pages
The remaining flour is 1-1 / 5 of this bag of flour = 4 / 5
Suppose this bag of flour weighs x kg
So x * (4 / 5) = 20
x=20*5/4=25
So this bag of flour weighs 25 kilos
Suppose the book has x pages
x-2x/3=40
x=120
1-1/5=4/5
20 / (4 / 5) = 25g
1： 120 pages
2： 4 / 5, 25kg
1. Suppose the book has x pages
2/3*x+40=x
x=120
2. Suppose there are x kg flour in this bag
1/5*x+20=x
x=25
The remaining flour is (1-1 / 5 = 4 / 5)
1.X=2/3X+40
Find x
2 4/5
X-X/5=20
Find x
The number of male students in a class is 2 / 3 of that of female students. What is the percentage of male students in the class?
2 / 5 suppose the number of boys is 2x and the number of girls is 3x, so 2x / (2x + 3x) = 2 / 5
Calculation (- 2 1 / 3) + (- 5 / 6) + (- 0.5) + (+ 1 1 1 / 6)
(- 2 and 1 / 3) + (- 5 / 6) + (- 0.5) + (+ 1 and 1 / 6)
= -14/6-5/6-3/6+7/6
= -19/6-3/6+7/6
= -22/6+7/6
= -5/2
Original formula = (- 2 and 1 / 3) + [(- 5 / 6) + (+ 1 and 1 / 6)] + (- 0.5)
=(- 2 and 1 / 3) + 1 / 3 + (- 0.5)
=[(- 2 and 1 / 3) + 1 / 3] + (- 0.5)
=(-2)+(-0.5)
=-(2+0.5)
=-2.5
Original formula = - 7 / 3-5 / 6-1 / 2 + 7 / 6
=-14/6-5/6-3/6+7/6
=-15/6
=-5/2
If the number of boys in a class is two-thirds of the number of girls, then the number of girls in this class is a fraction of the number of boys
Formula 3 △ 2
Answer: 3 / 2
If we divide the number of boys by five, we can take the number of girls as two thirds
It's easier to think like this: two boys and three girls. So the number of girls is three-thirds of that of boys
3 / 2........
If the number of boys is divided by 2 / 3, the number of girls is 1 / 3
The number of female students is equal to that of male students = 1 △ 2 / 3 = 3 / 2
If you don't understand, I'll ask you again. I wish you progress in your study and make progress! (*^__ ^ *
2/3
Divide 1 by 3 / 2
Help me solve a calculation problem; 1 / 4 / [(5 / 6-3 / 4) * 1.2 + 0.8]
1/4/[（5/6-3/4）*1.2+0.8]
=0.25/[(1/12)*1.2+0.8]
=0.25/(0.1+0.8)
=0.25/0.9
=5/18
There are 4 boys and 5 girls in group 1 of class 3 (2). What is the percentage of boys in the group? What's the percentage of boys in girls? What is the percentage of girls in the group?
Answer: Boys account for 49% of the total group, boys account for 45% of the total group, girls account for 59% of the total group
It is known that (1 + Tan α) (1 + Tan β) = 4cos (π / 3) 0
π/4
4cos（π/3）=4*1/2=2
(1+tanα)(1+tanβ)=1+tanαtanβ+tanα+tanβ=2
tanαtanβ+tanα+tanβ=1
tanα+tanβ/1-tanαtanβ=1=tan(α+β)
Zero
1+tanαtanβ+tanα+tanβ=2
tanα+tanβ=1-tanαtanβ
tan(α+β)=(tanα+tanβ)/(1-tanαtanβ)=1
Because 0