How Likely Is It?
Describe possible everyday events and the possible outcomes of chance experiments and order outcomes or events based on their likelihood of occurring; identify independent or dependent events.
Read this first
Some things are certain. Some cannot happen. Most sit in between.
Every event sits somewhere on this line.
Words you need
- Certain
- It will definitely happen.
- Impossible
- It cannot happen.
- Likely
- It will probably happen.
Worked example
e.g. Order these: rolling a 7 on a die, the sun rising, rolling an even number.
- A die has 1 to 6. There is no 7. So it cannot happen.
- The sun rises every day. That is certain.
- Three of the six numbers are even. That is an even chance.
- Order: roll a 7, roll an even number, the sun rises.
Count the ways it can happen. That tells you how likely.
Practice
The pictures fade as you go. By the last few you are on your own.
1Is rolling a number less than 7 certain or likely?with a picture
AnswerCertain. Every number on a die is less than 7.
2Is picking a red counter from a bag of 9 red and 1 blue likely?with a picture
AnswerVery likely. Nine out of ten are red.
3Is tossing a head on a coin an even chance?with a hint
Need a hint?
How many sides can it land on?
AnswerYes. Two sides, one head.
4You take a counter and keep it. Does that change the next pick?with a hint
Need a hint?
How many are left in the bag?
AnswerYes. There is one less counter.
5Is it impossible to roll a 0 on a normal die?on your own
AnswerYes. A die has 1 to 6.
6You toss a coin twice. Does the first toss change the second?on your own
AnswerNo. The coin does not remember.
7Name an event that is certain.on your own
AnswerTomorrow will come.
Think about it
1
What is the difference between a coin and a bag of counters?
One good answerA coin stays the same. Taking a counter out changes the bag.
2
Why is 'even chance' in the middle?
One good answerBoth things are just as likely as each other.
Common mistakes
Thinking a rare thing is impossible.
Rare means unlikely, not impossible.
Thinking a coin is 'due' a head.
Each toss starts fresh. The coin has no memory.