Chance and simple probability: Class 7 practice
When outcomes are equally likely, probability = favourable outcomes ÷ total outcomes. Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Fractions
The idea behind chance and simple probability
When outcomes are equally likely, probability = favourable outcomes ÷ total outcomes. It is between 0 (impossible) and 1 (certain).
Step-by-step method
- List all outcomes.
- Count the favourable ones.
- Write the fraction and simplify.
Worked example 1 (Basic)
A bag has 5 red, 5 blue balls. One is drawn at random. Find P(red).
- Total 10
- Red = 5
- P = 1/2
- Answer: 1/2
Worked example 2 (Standard)
A bag has 8 red, 9 blue and 6 green balls. One is drawn at random. Find P(red).
- Total 23
- Red = 8
- P = 8/23
- Answer: 8/23
Worked example 3 (Challenge)
A bag has 4 red, 1 blue and 4 green balls. One is drawn at random. Find P(not red).
- Total 9
- Not red = 5
- P = 5/9
- Answer: 5/9
Common mistakes and misconceptions
- Counting outcomes twice
- Giving probability greater than 1
Practice questions
- (Basic) A bag has 2 red, 4 blue balls. One is drawn at random. Find P(red).
- (Basic) A bag has 4 red, 6 blue balls. One is drawn at random. Find P(red).
- (Standard) A bag has 8 red, 5 blue and 8 green balls. One is drawn at random. Find P(red).
- (Standard) A bag has 5 red, 5 blue and 7 green balls. One is drawn at random. Find P(red).
- (Challenge) A bag has 4 red, 1 blue and 5 green balls. One is drawn at random. Find P(not red).
- (Challenge) A bag has 9 red, 3 blue and 3 green balls. One is drawn at random. Find P(not red).
Answer key with full working
- Q1: Total 6 → Red = 2 → P = 1/3 → Answer: 1/3
- Q2: Total 10 → Red = 4 → P = 2/5 → Answer: 2/5
- Q3: Total 21 → Red = 8 → P = 8/21 → Answer: 8/21
- Q4: Total 17 → Red = 5 → P = 5/17 → Answer: 5/17
- Q5: Total 10 → Not red = 6 → P = 3/5 → Answer: 3/5
- Q6: Total 15 → Not red = 6 → P = 2/5 → Answer: 2/5
Syllabus note
This skill is listed under "Data Handling" for Class 7 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.
Related practice and notes
Frequently asked questions
Which chapter is chance and simple probability in?
"Data Handling", Class 7 Maths (NCERT/CBSE). Other boards may place it differently.
How were the answers checked?
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.