Answer:
The total cost price will be the price of the helmet plus the tax added.
Answer:
Least cost per kilogram is "$5 for 2.0 kg"
Step-by-step explanation:
To get cost per kilogram, we divide the cost given by the kg given.
1. We need to divide 4 by 1.5 to get cost per kilogram.
Cost/Kg = 
2. We need to divide 5 by 2.0 to get cost per kilogram.
Cost/Kg = 
3. We need to divide 7 by 2.5 to get cost per kilogram.
Cost/Kg = 
4. We need to divide 8 by 2.5 to get cost per kilogram.
Cost/Kg = 
As we can see, the second option costs the least per kilogram.
I assume you mean one that is not rational, such as √2. In such a case, you make a reasonable estimate of it's position, and then label the point that you plot.
For example, you know that √2 is greater than 1 and less than 2, so put the point at about 1½ (actual value is about 1.4142).
For √3, you know the answer is still less than 4, but greater than √2. If both of those points are required to be plotted just make sure you put it in proper relation, otherwise about 1¾ is plenty good (actual value is about 1.7321).
If you are going to get into larger numbers, it's not a bad idea to just learn a few roots. Certainly 2, 3, and 5 (2.2361) and 10 (3.1623) shouldn't be too hard.
Then for a number like 20, which you can quickly workout is √4•√5 or 2√5, you could easily guess about 4½ (4.4721).
They're usually not really interested in your graphing skills on this sort of exercise. They just want you to demonstrate that you have a grasp of the magnitude of irrational numbers.
