7’s chris clements properties of number divisibility tests 8’s9’s
DESCRIPTION
Do you remember the divisibility test for multiples of 4? Divisibility Tests In this lesson you will learn divisibility tests for multiples of 7, 8 and 9. Divisibility test for multiples of 4 Look at the last 2 digits; are they even; if so when you half them are they still even.TRANSCRIPT
7’s
Chris Clements
Properties of Number
Divisibility tests
8’s9’s
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Learning Objective:
<Steps to success>
Do you remember the divisibility test for multiples of 4?
Divisibility TestsIn this lesson you will
learn divisibility tests for multiples of 7, 8 and 9.
Divisibility test for multiples of 4 Look at the last 2 digits; are they
even; if so when you half them are they still even.
Divisibility Tests for multiples of 8
The test for multiples of 8 is similar.
Do you know what changes must be made?
Divisibility test for multiples of 4 Look at the last 2 digits; are they
even; if so when you half them are they still even.
First look at the last 3 digits; 1272
*8 does not go exactly into 100 but does go into a 1000It’s even (so it is definitely a
multiple of 2)
If we half it;
It’s still evenso it must be a multiple of 4
If we wanted to test if 1272 is a multiple of 8
If we half it again;
It’s still evenso it
must be a
multiple of 8
Divisibility test for multiples of 8 Look at the last 3 digits; are they
even; if you half it, is it still even; if so, half it again, the answer must be
even.
Divisibility Tests
Give it a go;
Lets have a look at the first ten multiples of 9. 9, 18, 27, 36, 45, 54, 63, 72, 81, 90
What do you notice?
The digits add up to 9!
9, 1+8=9, 2+7=9, 3+6=9, 4+5=9, 5+4=9, 6+3=9, 7+2=9, 8+1=9, 9+0=9
Divisibility Tests for multiples of 9
Lets find multiples of 9 by doing the divisibility test; sum of the digits = 9.
This pattern continues; 9+9=9, 1+0+8=9, 1+1+7=9, 1+2+6=9,
1+3+5=9, 1+4+4=9…
This is the test for multiples of 7Divisibility
TestsFirst double the last digit
Subtract the rest of the number
Is 343 divisible by 7;1) 343 double the last digit = 62) 34 – 6 =2828 is a multiple of 7 so 343 is too
Answer must be a multiple of 7
Divisibility TestsFirst double the last digit
Subtract the rest of the numberAnswer must be a multiple of 7
Divisibility testsSteps to success
Divisibility test for multiples of 8 Look at the last 3 digits; are they
even; if you half it, is it still even; if so, half it again, the answer must be
even.Divisibility test for multiples of 9
Sum of the digits add up to 9.
Divisibility test for multiples of 7First double the last digit. Subtract the rest of the number. Answer must be a multiple of 7
Activity<type here>
Plenary
If this number sequence is extended will the number 2140 be in it. Give reasons.
This three digit number as factors of 2 and 7
Write anotherThree-digit
number that as factors of 2 and
7.