Transcript Time to Teach Presents

(National Numeracy Strategy)
(Based on DFES Lesson plans)
Resources
• Whiteboards and pen
• OHP calculator
• Set of calculators
Vocabulary
• multiple
• factor
• divisible by
Learning Objective
• Use tests of divisibility and factors
of numbers to inform and check
division calculations.
Mental Learning Task
A. 1 347  2
B. 2196  5
C. 22 211  3
Each of these division calculations will have
a remainder. Is this true or false?
Mental Learning Task
A. 1 347  2
B. 2196  5
C. 22 211  3
For A: 1347 is an odd number, so 1347 is
not divisible by 2.
Mental Learning Task
A. 1 347  2
B. 2196  5
C. 22 211  3
For B: 2196 does not end in a 5 or a 0, so
2196 is not divisible by 5.
Mental Learning Task
A. 1 347  2
B. 2196  5
C. 22 211  3
The digits sum to 8 and as 8 is not divisible
by 3, so 22211 is not divisible by 3.
Mental Learning Task
A. 1 347  2
B. 2196  5
C. 22 211  3
Use a calculator to confirm these slides.
Helpful Reminder
By the end of the lesson
children should be able to
• Use tests of divisibility and factors
of numbers to inform and check
division calculations.
Key idea
• Any odd number cannot be divisible
by an even number.
•A number is divisible by 3 if the
digits sum to a number that is divisible
by 3.
•A number is divisible by 4 if its last
2-digit number is divisible by 4.
•If the number 24 divides into a
number all factors of 24 will divide
into that number.
Main Learning Task
• Give out the calculators.
• Check this sum: 156  12 = 13
• This means 12 is a factor of 156
Main Learning Task
• Is 3 a factor of 156?
• As the digits of 156 add up to 12, and
12 is divisible by 3, 156 is divisible by
5.
• Check this using a calculator.
Main Learning Task
• What are the factors of 12?
• This means which numbers divide
exactly into 12.
• The factors are 1, 2, 3,4, 6 and 12.
Main Learning Task
• We know the factors of 12 are 1, 2, 3,
4, 6, and 12.
• Which of these factors do we know
will divide exactly into 156?
• Check these with your calculators.
Main Learning Task
198 18 = 11
• List the factors of 18 on your
whiteboards.
• Which of these factors also divide
into 198?
Main Learning Task
All these numbers are divisible by 4
124
128
264
304
144
1 000 024
312
636
484
23 446 344
What do you notice about all the
numbers you can see?
Main Learning Task
All these numbers are divisible by 4
124
128
264
304
144
1 000 024
312
636
484
23 446 344
All the 2- digit numbers can be divided
by 4.
Main Learning Task
All these numbers are divisible by 4
124
128
264
304
144
1 000 024
312
636
484
23 446 344
If you know this, the rest of the number must
be divisible by 4, no matter how big it is!
Main Learning Task
• Think of a 2-digit number that is
divisible by 4.
Main Learning Task
Put your two digit number on the end of this
number.
Divide the seven digit number by 4 using the
calculator.
Main Learning Task
• Four is a factor of this number.
• Is 4 a factor of any number where four is
the factor of the last two digits?
Plenary
A. 4 441  8
B. 11 105  15
C. 26 416  4
• Do any of these division calculations
leave a remainder?
Plenary
A. 4 441  8
B. 11 105  15
C. 26 416  4
• For D: Any number divisible by 8 must be
even. As 4441 is odd, it will not be divisible
by 8.
Plenary
A. 4 441  8
B. 11 105  15
C. 26 416  4
• For E: The factors of 15 are 1, 3, 5
and 15. If 11 1105 is divisible by 15, it
must be divisible by all factors of 15.
Plenary
A. 4 441  8
B. 11 105  15
C. 26 416  4
• Is 11 105 divisible by 3?
• Establish that 11 105 is not divisible by
3 because the digits do not sum to a
multiple of 3, so 15 is not a factor of
11 105.
Plenary
A. 4 441  8
B. 11 105  15
C. 26 416  4
• For F: Are the last two digits of
this number (16) divisible by 4?
Plenary
All these numbers are divisible by 6
624
102
456
2 448
216
270
• As all numbers are even, the
numbers must be divisible by 2.
Plenary
All these numbers are divisible by 6
624
102
456
2 448
216
270
• Add up the digits. As these sums are
divisible by 3, they are in the 3 times
table.
Plenary
All these numbers are divisible by 6
624
102
456
2 448
216
270
• As these numbers have the factors
of 2 and 3, they are divisible by 6.
Key idea
• Any odd number cannot be divisible
by an even number.
•A number is divisible by 3 if the
digits sum to a number that is divisible
by 3.
•A number is divisible by 4 if its last
2-digit number is divisible by 4.
•If the number 24 divides into a
number all factors of 24 will divide
into that number.
Children should now be able
to….
• Use tests of divisibility and factors
of numbers to inform and check
division calculations.
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