There is a pile of yellow sand on the construction site. One quarter of the total amount was used in the first day, and one quarter more was used in the second day than in the first day. How many tons of yellow sand are left

There is a pile of yellow sand on the construction site. One quarter of the total amount was used in the first day, and one quarter more was used in the second day than in the first day. How many tons of yellow sand are left

1/4x(1+1/4)=1/4x5/4=5/16
common
15÷（1-1/4-5/16）
=15÷7/16
=240 / 7 tons
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The analytic expression of the line y = - x + 2 with respect to the axis symmetry of the line x = 1

For x = 1 symmetry, then x becomes 1 × 2-x, that is 2-x
So y = - (2-x) + 2
y=x

In a workshop, the number of female workers was 35 less than that of male workers. Later, 17 male and female workers were transferred out, and the number of male workers was just twice that of female workers?

Number of male workers: 35 × 2 + 17, = 70 + 17, = 87; number of female workers: 87-35 = 52; answer: there were 87 male workers and 52 female workers

If the quadratic trinomial x ^ 2-kx-8 can be factorized in the range of real number, then the value of integer k is_____ .

Factorization by cross phase multiplication
1 -8
╳
1 1
K=-8+1=-7
Or:
Factorization by cross phase multiplication
1 8
╳
1 -1
K=8-1=7
If the quadratic trinomial x ^ 2-kx-8 can be factorized in the range of real number, then the value of integer k is 7 or - 7

In the school chorus, there are 8 boys more than 2 / 5 of the total number, and 4 girls less than 5 / 9 of the total number?
I want formulas, not equations!
In September, 1260 cars were actually sold, two seventh more than planned. How many more cars were actually sold than planned
The number of female students in a class is four fifths of that of male students. Later, a female student came in. As a result, the number of female students is five sixths of that of male students. How many students are there in the class now
Red, yellow and blue balloons have been prepared for the school on June 1. It is known that red balloons are one fifth less than yellow balloons, and yellow balloons are one fourth more than blue balloons. How many balloons have 100 schools prepared

（8-4）÷（1-2/5-5/9）
=4÷2/45
=90 people

Factorization of 4x2 + 4xy-3y2-8x + 3

=(2x+3y)(2x-y)-8x+3
=(2x+3y-1)(2x-y-3)

I hope there were 325 students in sixth grade last year. This year, there will be 15 more boys and one twentieth fewer girls. The total number will increase by six. How many boys are there this year?

There are 15 more boys and 1 / 20 fewer girls, and the total number of girls increases by 6, indicating that there are 9 fewer girls, that is, 1 / 20 of girls is 9, so the original girls are 9 / (1 / 20) = 180, and the original boys are 325-180 = 145
This year, there are 145 + 15 boys = 160

2x+y=4 5x_ 3y=_1

2X+Y=4 A
5X-3Y=1 B
3A+B
6X+3Y=12
+ 5X-3Y=-1
We get 11x = 11x = 1
X = 1 into a
2+Y=4 Y=2

The sum of the numbers a and B is 120, and the number a is 40. How many percent is the number a less than the number B? How many percent is the number B more than the number a?

B: 120-40 = 80
The number of a is less than that of B: 80-40 = 40
Number a is less than number B: 40 △ 80 × 100% = 50%
How many percent more than number a of number B: (80-40) △ 40 × 100% = 100%

The characteristics and properties of negative numbers
Urgent. Now, now

Negative numbers are always less than 0, less than positive numbers
The opposite number is positive, the absolute value is equal to its opposite number!