Special Numbers Maths

Special Numbers Maths

1. Divisability

   • 1
     • any whole number is divisible by 1
     • 2
       • Any even number is divisible by 2
       • 3
         • If the sum of the digits add up to a number that is divisible by three e.g 99= 9+9= 18
         • 4
           • a number is divisible by 4 if the last 2 digits are divisible by 4.  e.g. 248 48 is divisible by 4
           • 5
             • If it ends in 5 or 0
             • 6
               • if it is divisible by 2 and 3
               • 7
                 • no rule - just have to work it out
                 • 8
                   • if half of it is divisible by four.  e.g. 432/2= 216 and 16 is divisable by four
                   • 9
                     • if sum of digits are multiples of 9. 
                     • 10
                       • if the number ends in 0

2. Negative numbers rules!

   • + times + = +
     • + times - = -
       • - times + = -
         • - times - = +
   • + divided by + = +
     • + divided by - = -
       • - divided by + = -
         • - divided by - = +

3. Highest Common Factor

   • the HCF of 2 numbers is the largest factor common to both.  e.g. 21 and 35- HCF is 7 21: 1,3,7,21 35: 1,5,7,35

4. Lowest Common Multiple

   • the LCM is the lowest multiple of two numbers. e.g. 5 and 7 5: 5,10,15,20,25,30,357: 7,14,21,28,35LCM is 35

5. Factors= 12: 1,2,3,4,6,12

6. Multiples= 6: 6,12,18,24,30

7. Prime numbers

   • if a number is prime it will only have two factors. 1 and itself. 1 is not a prime number.
   • e.g. 149
     • To test if 149 is prime. try to divide it by the prime numbers. the prime numbers are below. 
     • PRIME NUMBERS!
       • 2,3,5,7,11,13,17,19,23,29

8. Factor Tree

   • 32
     • 2x2= 4 4x2=8 8x2=16 16x2=32 32= 2x2x2x2
     • 4
       • 2
       • 2
     • 8
       • 4
         • 2
         • 2
       • 2

9. Squares number, cube numbers, square roots, cube roots

   • Squares
     • A square number is the product of a factor times by itself
     • cubes
       • a cubed number is the product of a number times by itself and then times by itself again.
       • square roots
         • the square root of 16 is 4 because 4 times 4 is 16. 
         • cube roots
           • The cubed root of 25 is 5 because 5 times 5 times 5 is 25. 
           • triangular numbers
             • Triangle of dots. 1,3,6,10,15,21,28 etc
             • Square numbers
               • they are called square numbers because they are like the area of a square. 1,4,9,16,25,36 etc