Special Numbers Flashcards
Divisibility Rule for 2
Any even integer - a number whose last digit is 0, 2, 4, 6 or 8.
Divisibility Rule for 3
Any integer where the sum of the digits is a multiple of 3.
Divisibility Rule for 4
Any even integer whose last two digits are divisible by 4.
Divisibility Rule for 5
Any integer whose last digits is a 0 or a 5.
Divisibility Rule for 6
Any even integer which is divisible by 3 and 2.
Divisibility Rule for 8
Any even integer whose last 3 digits are divisible by 8.
(halve the last 3 digits three times - did you get a whole number?)
Divisibility Rule for 9
Any integer where the sum of digits is divisible by 9.
Divisibility Rule for 10
Any integer whose last digit is 0.
How do you check for divisibility for larger numbers?
By splitting them into coprime factors
e.g. to test for divisibility by 12 test for divisibility by 3 and 4.
Is 1 a prime number?
NO!!!
definition of a prime number
a whole number greater than 1 that cannot be exactly divided by any whole number other than itself and 1
definition of a factor
a number that divides another number evenly, with no remainder
definition of a multiple
the numbers you get when you multiply a certain number by an integer
How do you list all the factors of a number systematically?
By dividing the number by each counting number, starting with 1
How do you write a number as a product of its prime factors using a factor tree?
- Write the number at the top of the factor tree.
- Draw two branches from the number to split the number into a pair of factors, greater than 1.
- Write each factor at the end of each branch.
- This process continues until the branches all end in prime numbers.
How do you find the highest common factor (HCF) of 2 numbers?
The highest common factor is found by multiplying all the factors which appear in both lists
How do you find the lowest common multiple (LCM) of 2 numbers?
List out all multiples of both numbers and highlight the LCM
How do you use a Venn Diagram to find the HCF & LCM of 2 numbers?
- Break the numbers into the product of prime factors using prime factor trees, as before.
- Put each prime factor in the correct place in the Venn diagram. Any common factors should be placed in the intersection of the two circles.
The highest common factor (HCF) is found by multiplying together the numbers in the intersection of the two circles.
The lowest common multiple (LCM) is found by multiplying together the numbers from all three sections of the circles.
definition of an integer
a number that is not a fraction; a whole number.
definition of a perfect number
a positive integer that is equal to the sum of its proper divisors.
definition of a square number
the product of a number multiplied by itself
definition of a cube number
a number that has been multiplied by itself and then multiplied by itself again.
definition of a triangular number
a number that can be represented by a pattern of dots arranged in an equilateral triangle with the same number of dots on each side.
How do you multiple and divide decimals?
Remove the decimal place, complete the calculation, put the decimal place back.
