Tagged:

• Creator
Topic
• #14856
Keymaster
Post count: 802

A box contains blue, red and white marbles. Write an algebraic expression for:
a.
The probability of a blue marble.

b. The probability of a blue or white marble.
c. the Probability for a not blue marble.

total amount of marbles = b + r + w

a. P(B) = $$\frac{b}{b+r+w}$$

b. P(B or W) = $$\frac{b+w}{b+r+w}$$

c. P(not B) = $$\frac{r+w}{b+r+w}$$

• Author
Replies
Keymaster
Post count: 802

For a guessing competition, a jar contains 5 red marbles and an unknown number of white marbles. Jason selected a marble at random from the jar, recorded its colour, and then replaced the marble in the jar. He repeated this procedure until he had made 200 draws. His results showed a red marble being selected 17 times. Predict the total number of marbles in the jar.

he got 17/200 red, so that should be the same as 5/x since they would be in the same proportion.

we get this equation: $$\frac{5}{x}=\frac{17}{200}$$

Flip both sides to make it easier

$$\frac{x}{5}=\frac{200}{17}$$

$$x=5\times\frac{200}{17}$$

x = 58.8

so approximately 59 marbles in

Keymaster
Post count: 802

Tracey is twice as likely to solve a maths problem as Terry is. If Tracey has a 25% chance of solving the problem. What are the chances of both Terry and Tracey solving the problem?

If Tracey is twice as likely as Terry, that means the Terry is half of Tracey.
Half of 25% is 12.5%
converting these to decimals P(Tracey Right) = 0.25
P(Terry Right) = 0.125
P(both are right) = 0.25 × 0.125
= 0.03125 =
3.125% or 132

Keymaster
Post count: 802

In a game of football, Team A has a 41% chance of beating Team B, while team B has a 51% chance of beating Team A.
a. What is the other outcome?
b. What is the probability of this outcome?

a. Draw
b. Team A has a 41% chance of winning
P(Win) = 41%
Team B has a 51% chance of winning which means Team A has a 51% chance of losing
P(Lose) = 51%
the probability of a draw will be 100% – 41% – 51%
= 8%

∴ P(Draw) = 8%