This document discusses divisibility tests for numbers 2 through 10 and powers of 10. It explains the tests for each number, such as a number being even to be divisible by 2, or having a digit sum of 9 to be divisible by 9. An example problem is given to find 3 numbers that multiply to 150, and the document walks through using divisibility tests to determine the numbers are 2, 3, and 25.
Divisibility tests
These aresimple tricks to test what a number can
be shared by .
We are going to learn tricks for testing if a
number can be shared by 2, 3, 4, 5, 6, 8, 9, and
multiples of 10.
2.
Divisibility tests
x x= 150
This is a typical SATs question that can be solved
by divisibility tests.
Here we are asked to list 3 numbers that can be
multiplied to make 150. Think about it. We will
come back to this question after we learn our
skills.
Divisibility tests
Divisible by3?
If a number is divisible by 3…
It’s digit sum is 3, 6, or 9.
The digit sum is when you add the digits in the
number repeating until you get to 1 digit.
7.
Divisibility tests
Divisible by3?
So the number 1467 has a digit sum of 9
1 + 4 + 6 + 7 = 18 then 1 + 8 = 9
So 1467 is divisible by 3.
Divisibility tests
Divisible by4?
If a number is divisible by 4…
If we half the number, and the result is even,
then our number is divisible by 4.
10.
Divisibility tests
Divisible by4?
If a number is divisible by 4…
If the last 2 digits of a number are divisible by 4,
then our number is as well.
4 655 728 is divisible by 4 because 28 is divisible
by 4.
Divisibility tests
Divisible by6?
If a number is divisible by 6…
It passes the tests for both divisibility by 2 and
divisibility by 3.
In other words – an EVEN number with digit sum
3, 6 or 9
Divisibility tests
Divisible by7?
If a number is divisible by 7…
It appears in the 7 times table!
Sorry! You’ll just have to learn it because there is
no trick for 7s!
Divisibility tests
Divisible by8?
If a number is divisible by 8…
If you halve it, and halve it again, the result is an
even number.
If the last 3 digits are divisible by 8, the whole
number will be.
19.
Divisibility tests
Divisible by8?
If a number is divisible by 8…
So 2, 560, 104 is divisible by 8 because 104 is
divisible by 8.
( 104 ÷ 2 = 52 52 ÷ 2 = 26 26 is EVEN. )
Divisibility tests
Divisible by…?
2: ends with 2, 4, 6, 8, or 0
3: digit sum is 3, 6, or 9
4: halve last 2 digits and the result is even
5: ends with 5 or 0
6: ends with 2, 4, 6, 8, or 0 AND digit sum is 3, 6, or 9
7: -
8: Halve the last 3 digits twice, and the result is even.
9: digit sum is 9
10: ends with 0
29.
Divisibility tests
x x= 150
Remember this question…
Test 150 to see what can go in the boxes.
30.
Divisibility tests
x x= 150
Remember this question…
150 is divisible by 2, 3, 5, 6, and 10 amongst
other numbers (pick any one for the first box)