This seems to be referring to a particular construction of the perpendicular bisector of a segment which is not shown. Typically we set our compass needle on one endpoint of the segment and compass pencil on the other and draw the circle, and then swap endpoints and draw the other circle, then the line through the intersections of the circles is the perpendicular bisector.
There aren't any parallel lines involved in the above described construction, so I'll skip the first one.
2. Why do the circles have to be congruent ...
The perpendicular bisector is the set of points equidistant from the two endpoints of the segment. Constructing two circles of the same radius, centered on each endpoint, guarantees that the places they meet will be the same distance from both endpoints. If the radii were different the meets wouldn't be equidistant from the endpoints so wouldn't be on the perpendicular bisector.
3. ... circles of different sizes ...
[We just answered that. Let's do it again.]
Let's say we have a circle centered on each endpoint with different radii. Any point where the two circles meet will then be a different distance from one endpoint of the segment than from the other. Since the perpendicular bisector is the points that are the same distance from each endpoint, the intersection of circles with different radii isn't on it.
4. ... construct the perpendicular bisector ... a different way?
Maybe what I first described is different; there are no parallel lines.
Answer:
You have 2 and 1/2 pizzas and your friend has 5/6 of a pizza.
Step-by-step explanation:
You have 3 1/4 pizzas. If you get rid of 3/4 of a pizza, you will end up with 2 2/4 pizzas.
To make it easier, you can just change the values into improper fractions: 3 1/4 = 13/4
13/4 - 3/4 = 10/4
10/4 = 2 2/4 pizzas
(2 2/4 = 2 1/2)
Anyways! You now have 2 and a half pizzas. You have 3 times the amount of pizza that your friend has. In other words, your friend has 1/3 the amount of pizza that you have. You can solve for this in two ways, whichever way you solve it is up to you.
- You can solve this problem by dividing the amount of food you have by 3:
which equals 0.8333... (the 3 is repeating). But you can just keep your final answer in fraction form if you want to: 
- You can solve this problem by multiplying 1/3 to the amount of food you have:

You have 2 and 1/2 pizzas and your friend has 5/6 of a pizza.
June=1,225
April=1,225
May=1,225
All June April and May is 3,675 haircuts
Answer:
4
Step-by-step explanation:
- If you take the lowest half of the data (from the lower extreme to the median) and find the median of these numbers, that is called the lower quartile or quartile 1.
- If you take the upper half of the data (from the upper extreme to the median) and find the median of these numbers, that is called the upper quartile or quartile 3.
- The interquartile range is the difference between quartile 1 and quartile 3.
- 4, 5, 6, 8, 9, 10, 11, 13
- Median=8.5
- Q1=6.5
- Q3=10.5
- 10.5-6.5=4
I also added my PowerPoint if you didn't get what I was saying.
Answer:
19 in the largest prime number smaller than 20.
52x19=988.
Step-by-step explanation: