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NCERT Class 9 Mathematics Exercise Set 7.1 Solutions: The Mathematics of Maybe: Introduction to Probability
AI-written, checked on 23 Oct 2026
Solutions written by Shishya, checked — not the board's official answers
Step-by-step working for every question of Exercise Set 7.1 in NCERT's Class 9 Mathematics book, chapter “The Mathematics of Maybe: Introduction to Probability”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.
How these were checked: the solutions were drafted with AI and then read and corrected on 23 Oct 2026. Every numerical final answer is recomputed from the question's own numbers by a calculator check that runs before each release; proofs and explanations were read, not machine-checked. The NCERT textbook is the authority — if something here disagrees with it, follow the book.
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Ex 7.1 Q1
Place each event on the 0 (impossible) to 1 (certain) scale and label it impossible, less likely, even chance, more likely or certain, with a reason: (i) next Monday comes after Sunday; (ii) snow in Mumbai in July; (iii) an elephant walks through your classroom today; (iv) you greet at least one friend at school tomorrow.
- (i) Since the calendar cycle is fixed, Monday always follows Sunday, making this event certain with a probability of 1.
why?
Probability of an event = number of outcomes in its favour ÷ total number of equally likely outcomes. It is always from 0 (impossible) to 1 (certain).
- (ii) July is the monsoon season in Mumbai and the city is warm all year; snow there in July has never been recorded, so this is impossible, probability 0.
why?
Probability of an event = number of outcomes in its favour ÷ total number of equally likely outcomes. It is always from 0 (impossible) to 1 (certain).
- (iii) An elephant walking through a classroom is not impossible but is extremely rare, making it a less likely event with a probability close to 0.
why?
Probability of an event = number of outcomes in its favour ÷ total number of equally likely outcomes. It is always from 0 (impossible) to 1 (certain).
- (iv) Greeting at least one friend at school is a common daily occurrence for most students, making it a more likely event with a probability close to 1.
why?
Probability of an event = number of outcomes in its favour ÷ total number of equally likely outcomes. It is always from 0 (impossible) to 1 (certain).
Answer: (i) certain; (ii) impossible; (iii) less likely; (iv) more likely
- (i) Since the calendar cycle is fixed, Monday always follows Sunday, making this event certain with a probability of 1.
Other exercises in this chapter
- Exercise Set 7.2 — 6 questions
- Exercise Set 7.3 — 3 questions
- Exercise Set 7.4 — 2 questions
- End-of-chapter exercises — 16 questions
← The Mathematics of Maybe: Introduction to Probability: notes, practice and all exercises
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