Answer:
30%
Step-by-step explanation:
Before starting to solve this question we have to understand the following. 1% is equal to one hundredth of something whole, and can be write as 
.
Now in order to solve this question we will first have to find a fraction that represent how much student out of the whole class choose hamburgers. We can easily find this fraction since the numerator of the fraction will be equal to the number of people that choose hamburgers and the denominator will be equal to the number of all students in the class. So we get......
Now in order to find out what percentage will this fraction equal to we will have make a fraction with the same value but with a denominator being 100. To do that we will have to understand the following......
(m is any number except 0)
The main I idea of this rule is that if we multiply the numerator and the denominator by the same number (any number except 0) we will get a fraction with the same value but with a different denominator and numerator.
So in our case we we do the following.........
(multiply both numerator and the denominator by 10 and we get...)
Now if we go back to what I said at the start of my explanation we will understand that another way of writing down 
is 30%.
Answer:
Second option: 81y^4 - 16x^2, the difference of squares
Step-by-step explanation:
(9y^2-4x)(9y^2+4x) is a special product named difference of squares, then we can apply this formula:
(a-b)(a+b)=a^2-b^2, with a=9y^2 and b=4x, then:
(9y^2-4x)(9y^2+4x)=(9y^2)^2 - (4x)^2
(9y^2-4x)(9y^2+4x)=(9)^2 (y^2)^2 - (4)^2 (x)^2
(9y^2-4x)(9y^2+4x)=81y^(2*2) - 16x^2
(9y^2-4x)(9y^2+4x)=81y^4 - 16x^2
Answer: 2
8 to the power of 1/3 is 2.
Step-by-step explanation:
Given expression:
2x(x + 7)-(3x +1);
To distribute implies to spread a process equally in an expression. Often times, the distributive property is used for expressions inside parentheses;
2x(x + 7)-(3x +1)
Distribute 2x over the first parentheses;
the negative sign distributes over the second part
= (2x² + 14x) - 3x -1
= 2x² + 14x -3x -1
Add like terms;
= 2x² + 11x -1
This expression 2x² + 11x -1 is equal to the given one
50%. students (in percent) who passed the second exam also passed the first exam.
Let's imagine that there are 100 kids in the teacher's class. We know that 40 of them passed BOTH tests, and 80 passed the second test.
Because if they weren't, they wouldn't have passed the first test and consequently wouldn't have passed both, we can be sure that the group of students who passed BOTH tests is only made up of the 80 who passed the second test.
Thus, both tests were passed by 40 of the 80 pupils who passed the second one:
40/80 = 1/2 = 50%.
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