PLAYING WITH NUMBERS PLAYING WITH NUMBERS IN THIS
PLAYING WITH NUMBERS
PLAYING WITH NUMBERS IN THIS CHAPTER YOU WILL LEARN FACTORS AND MULTIPLES TEST FOR DIVISIBILITY OF NUMBERS BY 10, 5, 2, 3, 6, 4, 8, 9, 11 HIGHTEST COMMON FACTORS (HCF) LOWEST COMMON MULTIPLES (LCM) PROBLEMS BASED ON ABOVE
FACTORS AND MULTIPLES FACTORS OF A NUMBER IS EXACT DIVISOR FOR EXAMPLE: THE FACTORS OF 8 ARE 1, 2, 4, 8 12 ARE 1, 2, 3, 4, 6, 12 MULTIPLES FOR EXAMPLE: THE MULTIPLES OF 9 ARE 9, 18, 27, 36… 10 ARE 10, 20, 30, 40, 50…
PRIME NUMBERS, COMPOSITE NUMBERS PRIME NUMBERS The numbers which are divisible 1 and itself is called Prime Number. 1 is not prime number For Example 2, 3, 5, 7, 11, 13, 17, …. . COMPOSITE NUMBER The number which have more than two factors are called Composite number For example 4, 8, 9, 10, 12, 14, 16, …. .
TEST FOR DIVISIBILITY OF NUMBERS DIVISIBILITY TEST BY 10 If a number has 0 at ones place then it is divisible by 10 For Example 40, 870, 3457290 etc DIVISIBILITY TEST BY 5 If a number which has 0 or 5 in its ones place is Divisible by 5 For Example 1750125 is divisible by 5
DIVISIBILITY TEST CONT. … DIVISIBILITY TEST BY 3 If the sum of the digits is a multiple of 3 , then the number is divisible by 3 For Example 7221 is divisible by 3 DISIBILITY TEST BY 6 If a number is divisible by 2 and 3 both then it is divisible by 6 For Example 18, 36, 42, 48 etc DIVISIBILITY TEST 4 A number with 3 0 r more digits is divisible by 4 if the Formed by its last two digit is divisible by 4 For Example 6783624 is divisible by 4
For example 61809 is divisible by 11 HOW TO FIND OUT HCF Find the prime factors of the given number and Then take common numbers among them For example The HCF of 27, 81, 162 is 27=3 x 3 x 3 81=3 x 3 x 3 x 3 162=2 x 3 x 3 So the HCF of above =3 x 3 x 3, Answer is 27
HOW TO FIND OUT LOWEST COMMON MULTIPLE (LCM) For Example Find the LCM of the 850=2 x 5 x 5 x 17 680=2 x 2 x 2 x 5 x 17 The lowest common factors are 2 x 2 x 2 x 5 x 5 x 17 Answer= 34000
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