Step-by-step explanation:
Before we answer, the area of a Circle given it radius is

The area of a circle given it diameter is

So let answers question 1-4.
1. The area is

2. The area is

3.

4.

For the 5th problem, circumference is

where d is the diameter and

where r is the radius.
A circumference of 100 m means the radius is 50 because


So this means the area is

Answer:
4x-20 is the same as x+x+x+x-20
Answer: Mrs.Buller collects a 500-ml sample of seawater for her chemistry class, and it has 1.94% of chlorine, we have to determine the amount of chlorine in the sample:

Therefore the chlorine content in 500ml of water is 9.7ml.