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:
10 km/h
Step-by-step explanation:
First, convert 150 minutes to hours:
150/60
= 2.5 hours
Then, to find his speed, divide the km by the number of hours:
25/2.5
= 10 km/h