Grade 8 Probability Quiz 2 draws its questions at random from 32 questions across these topics:
A few of the question types, with full solutions, so you know what to expect.
The language of chance. An event has a probability of \(0,5\). What does this tell you?
Answer: There is an even chance - the two outcomes are equally likely
Probability runs from \(0\) (impossible) to \(1\) (certain).
\(0,5\) sits exactly halfway, so the event is just as likely to happen as not.
Tip: Tossing a fair coin is the classic example of an even chance.
The language of chance. An event is unlikely, but it is still possible. Where does its probability sit on the probability scale?
Answer: Between \(0\) and \(0,5\)
"Possible" rules out \(0\), because \(0\) means it can never happen.
"Unlikely" means it is less likely than not, so it sits below \(0,5\).
The language of chance. The probability that it will rain tomorrow is \(0,9\). This event is:
Answer: Very likely
\(0,9\) is very close to \(1\), but it is not equal to \(1\).
So the event is very likely - but still not guaranteed.
Tip: Only a probability of exactly \(1\) may be called certain.
The language of chance. Which of these events is CERTAIN?
Answer: Rolling a number less than \(7\) on a fair six-sided die
The faces are \(1; 2; 3; 4; 5; 6\) - every one of them is less than \(7\).
All \(6\) outcomes are favourable, so \(P = \dfrac{6}{6} = 1\).
Tip: Rolling a \(7\) is the opposite - it is impossible, so \(P = 0\).
The language of chance. Which of these probabilities is the GREATEST?
Answer: \(0,3\)
Write them all as decimals so you can compare them fairly.
\(\dfrac{1}{4} = 0,25\) \(20\% = 0,2\) \(\dfrac{1}{10} = 0,1\)
Now compare: \(0,3 > 0,25 > 0,2 > 0,1\)
Tip: Never compare a fraction with a percentage directly - convert both first.