Answer:
a) 
b) 
Step-by-step explanation:
Number of balls in the urn = 12
Number of white balls in the urn = 4
So, number of balls which are not white = 12 - 4 = 8
We know that probability = No. of outcomes/Total number of outcomes
Let 
denotes the event of getting white ball by A, B and C
a) each ball is replaced after being drawn.
Probability = Number of white balls/Total number of balls
Solution: 
b)the balls that are withdrawn are not replaced.
Solution:
If A wins: 
If A lost and B wins: 
If A and B lost and C wins: 
and so on....
Answer:
Step-by-step explanation:
To solve this problem you need the function
h(t) = -16t2 + v0t + h0
where t = time
v0 is the initial velocity, which in our case is 0
h0 = initial height, which in our case is 256
h(t) = 0 since we want to know when the ball will hit the ground.
0 = -16 t2 + 256
And we can solve for t
If we rearrange the terms we see that this is a difference of 2 squares
0 = 256 - 16t2
0 = (16-4t)(16+4t)
Setting each factor = 0
16-4t=0 16+4t=4
t = 4 t = -4
The second solution is discarded as time cannot be negative.
So the ball will hit the ground in 4 seconds.
It depends on what you are trying to calculate but the most common way I go to find percentage is to multiply by the number in decimal for ie. 50% = .5.
If you are looking for a way to do it quickly in your head I always take find out what 10% is like in the case of 100 it would be 10 so if I want to find 15% I know I can find 10% and if I cut what 10% is in half I will find 5% so likewise if I add what 10%+5% I will end up with 15%. For example, 10% of 100 is 10 half of 10 is 5 and 10+5 equals 15. If you need to find something like 20% or 30% I know that I can find 10% and instead of dividing(cutting it in half) I can multiply by 2 or 3. 10% + 10% =20%
I hope it helps, if you have more questions let me know!
