Number system

Types of numbers, divisibility, HCF and LCM.

General Test5 questions
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Key ideas

  • Natural, whole, integer, rational and irrational numbers.
  • Prime numbers have exactly two factors; 1 is neither prime nor composite.
  • Divisibility: by 3 if the digit sum is divisible by 3; by 9 if it is divisible by 9; by 4 if the last two digits form a multiple of 4; by 11 if the alternating digit sum is a multiple of 11.
  • HCF × LCM = product of two numbers.

Practice questions

What is the HCF of 36 and 48?Easy
What is the LCM of 12 and 18?Easy
The number 1 is:Easy
Which number is divisible by 9?Medium
The HCF of two numbers is 6 and their product is 432. What is their LCM?Medium
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