Edexcel IGCSE Math B 1.B Prime Numbers, Factors & Multiples Question Bank

Practise prime factorisation, HCF and LCM, including algebraic prime products and square-number conditions.

Exam points

select minimum prime powers for HCF and maximum powers for LCM
retain algebraic factors when writing HCF or LCM as a prime-factor product
pair odd prime exponents with the least multiplier needed to form a square

[Maximum number: 1]

Figure for Question 1.B Prime numbers, factors and multiples question 1 — Edexcel IGCSE Math B

Ahmed and Hani play a game with 20 numbered balls.
The 20 balls are numbered from 1 to 20.
The balls are put in a bag.
Ahmed takes at random a ball from the bag, makes a note of its number and puts the ball back into the bag.
If the number is a multiple of 5, Ahmed wins.
If Ahmed does not win, Hani takes a ball, replaces it, and wins if the number is a multiple of 3.
If Hani does not win, Ahmed takes a ball, replaces it, and wins if the number is a multiple of 6.
If Ahmed does not win, Hani takes a ball, replaces it, and wins if the number is a multiple of 4.
If Hani does not win, the game stops and the result is a draw.

Write down all the multiples of 3 lying between 1 and 20.

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1.B Prime numbers, factors and multiples question 1