Number Flashcards
What are the first 5 prime numbers?
Is the number 1 a prime number?
3, 5, 7, 11, 13
No it’s a special number (multiplicative identity)
How do you know if a number is divisible by 3?
Eg 39123
If it’s digits add up to a number that is divisible by 3.
39123= yes it is because. 3+9+1+2+3 = 18 ( which is divisible by 3)
How do you know if a number is divisible by 11?
Add, subtract, add the digits together and if divisible by 11.
Example 418
4-1+8=11. Yes
Count up in square numbers.
1,4,9,16,25,36,49,64,81
100,121,144
13x13=
169
Count up in cubes
1, 8, 27, 64, 125, 396
4x6+4x5= …..x(6+5) -what is the missing number
4 is the missing number i.e. 4x(6+5)
A quick way of multiplying 21 x 7
break up the 21 into 10 and 11 and multiple both by 7
ie. 21 x 7 = 10 x 7 + 11 x 7
= 70 + 77
= 147
What is the order of operations?
- do operations with grouping symbols
- do multiplication and division as they appear (left to right)
- do addition and subtraction as they appear (left to right)
Any number that is divisible by 5 will end in …?
zero or a 5
i.e. both 30 and 45 are divisible by 5
Is this true? 8 x (15 +5) = (8x 15) + (8 x 5)
True!
any multiplication can be done by breaking the number into addition of seperate parts
Is this true?
116 / 4 = (100 /4) + (16 /4)
True!
any division can be done by breaking the number into addition of seperate parts
What are the five triangular numbers
1, 3, 6, 10, 15
What are the 6 Fibonacci numbers
1, 1, 2, 3, 5, 8
write 252 as a product of its prime numbers .
252= 2x2x3x3x7
= 2^2x3^3x7
