Answer:
The correct options are 1, 3 and 4.
Step-by-step explanation:
We need to find the expressions whose simplified form is a rational number.
Rational number: If a number is defined in the form of p/q where p and q are integers and q≠0, then it is called a rational number.
For example: 0,2, 4.3 etc.
Irrational number: If a number can not defined in the form of p/q, where p and q are integers and q≠0, then it is called an irrational number.
First expression is

12 is a rational number.
Second expression is

is an irrational number.
Third expression is

21 is a rational number.
Fourth expression is

5 is a rational number.
Therefore, the correct options are 1, 3 and 4.
Answer:
the fourth one is correct
Increase with a 28% change
Part A: There are five buttons in all in all in the given item. The item above can be answered through the fundamental principles of counting.
There are 5 items to choose from during the first pick. Because the shape can be returned and picked again, there are also 5 items to choose from in the second pick. Multiplying them,
n = 5 x 5 = 25
Therefore, the sample size for the compound event is equal to 25.
Part B: The same concept can be used in this part of the item; however, instead of 5 there are 6 buttons to choose from.
n = 6 x 6 = 36
Hence, the sample size of this picking process is 36.
<span>1/5
This is a matter of elimination. So let's figure out how many of each display there is.
30% of 150 = 0.30 * 150 = 45 displays about electricity.
2/5 * 150 = 0.40 * 150 = 60 displays about renewable energy
1/10 * 150 = 150/10 = 15 displays about gas.
The rest of the displays are about nuclear power. So
150 - 45 - 60 - 15 = 30 displays about nuclear power. Since we want a fraction, we get 30/150
But 30/150 isn't in it's simplest form. The largest number that will evenly divide both 30 and 150 is 30. So divide both the numerator and denominator by 30
(30/30)/(150/30) = 1/5
So 1/5 of the displays are about nuclear power.</span>