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Ex 3.2, 11 - Chapter 3 Class 6 Playing with Numbers
Last updated at Dec. 16, 2024 by Teachoo
Prime and Composite Numbers
Chapter 3 Class 6 Playing with Numbers
Concept wise
- Factors and Multiples
- Perfect number
-
Prime and Composite Numbers
- Sum of prime numbers
- Prime numbers from 1 to 100
- Divisibility Tests - Divisibility by 5, 10, 2
- Divisibility Tests - Divisibility by 4, 8
- Divisibility Tests - Divisibility by 3, 6, 9
- Divisibility Tests - Divisibility by 11
- Divisibility Tests - All
- Common Multiples
- Common Factors
- More Divisibility Rules
- Factor Tree
- Prime Factorisation
- Highest Common Factor
- Lowest Common Multiple
- Statement questions on LCM
- Statement questions on HCF
Transcript
Ex 3.2, 11 Write five pairs of prime numbers less than 20 whose sum is divisible by 5. (Hint : 3 + 7 = 10)Numbers divisible by 5 are 5, 10, 15, 20, 25, 30 (All these are also called multiples of 5) We need to write these as sum of 2 prime numbers less than 20 i.e. using 2, 3, 5, 7, 11, 13, 17, 19 (1) 5 = 2 + 3 (2) 10 = 3 + 7 (3) 15 = 2 + 13 (4) 20 = 3 + 17 (5) 20 = 7 + 13 So Pairs are (2, 3) ; (3, 7) ; (2, 13) ; (3, 17) ; (7, 13) (Both 2 and 3 are prime) (Both 3 and 7 are prime) (Both 2 and 13 are prime) (Both 3 and 17 are prime)
