Answer:
The probability that the counter was blue is 
Step-by-step explanation:
Number of black Counters = 5
Number of blue Counters = 4
Number of white Counters = 1
We need to write down the probability that the counter was blue.
First find Total Counters
Total Counters = Number of black Counters + Number of blue Counters + Number of white Counters
Total Counters = 5+4+1
Total Counters = 10
Now, we need to find probability that the counter taken was blue
The formula used is:

There are 4 blue counters in the back, so Favourable outcomes = 4

The probability that the counter was blue is 
Assuming BOD and AOC are straight lines.
Area of the rectangle = 4 x ΔAOD
Area of the rectangle = 4 x 10
Area of the rectangle = 40 unit²
Area of ΔABC = 1/2 x 40
Area of ΔABC = 20 unit²
Step-by-step explanation:

2. Use rise over run to find it
Answer:
r=C/2π
Step-by-step explanation:
here we just have to rearrange the given formulae in such a way that it finds out the value of r.
Given formulae is C=2πr
we can carry 2π to the left hand side.
r=
. is the recquired formulae.