Probability Trees - See linked image
A good visual method for this is a probability tree.
Each set of branches represents the probabilities of on coin being removed, the second set is out of 9 as the first coin is taken and not replaced.
Multiply along the lines to work out the probability of each of the combinations.
*Even though only 'Dime Dime' is needed, it is best to do all of them as this way you are able to get all marks in an exam; you can also add up all the final values as a check to see if you are right.
Answer:
The slope is -1/4
Step-by-step explanation:
perpendicular line is 
25² = ( 20 + 5 )² This is the square of a binomial:
( a + b )² = a² + 2 a b + b²
625 = 20² + 2 · 20 · 5 + 5²
625 = 400 + 200 + 25
625 = 625 ( correct )
The Answer to this problem is BN=3.8 Units.