2 Complements to 100 and 1000
Number
boards
Use Number Boards, with knowledge of addition and subtraction facts and place
value, to derive sums and differences of multiples of 5, 10 and 100.
Objectives central to the
activity:
• U & A Solve one- and two-step
problems involving numbers
• U & A Describe and explain
What to do first
Open Number Boards. Click on Explore
then Number. Select 6 columns, 6
rows. Click on Pre-sets and then select
Complements to 100, Multiples of 5.
Make board.
methods, choices and solutions to
puzzles and problems, orally and in
writing, using pictures and diagrams
• Use knowledge of addition and
subtraction facts and place value to
derive sums and differences of pairs
of multiples of 10, 100 or 1000
• S & L Explain a process or present
information ensuring that items are
clearly sequenced and that relevant
details are included.
Key vocabulary
calculate, calculation, method,
explain, pattern, relationship, add,
subtract, sum, total, difference, plus,
minus
Children will be building on
their ability to:
• recall addition and subtraction facts
for each number to 20
• say a subtraction fact that is the
inverse of an addition fact, and a
multiplication fact that is the inverse
of a division fact, and vice versa.
This board is covered in pairs of
numbers that will sum to 100. How
does knowing the addition bonds to
ten help with some of them?
After some discussion take feedback.
Confirm that knowing 5 + 5 = 10 helps
to calculate 50 + 50 = 100 or 6 + 4 helps with 60 + 40. Use examples as
necessary.
Invite volunteers to highlight the
relevant pairs on the board using the
colour palette.
Note Check must be used after each
pair is entered.
Highlight several pairs that are
multiples of ten and emphasise the
related bond to ten. How do the
complements to 100 we have entered
help with the numbers on the board
that have 5 ones/units?
After some discussion in pairs use
children’s ideas to explore how 70 + 30
helps with
75 + 25 using (70 + 5) + (30 2 5)
or 65 + 35 using (70 2 5) + (30 + 5).
Model a range of examples that
children offer. Highlight the numbers
on the board.
Use Check to confirm the totals.
Use Settings to return to the set-up screen. Select 6 columns, 6 rows.
Click on Pre-sets and then select Complements to 1000, Multiples of 50.
Make board.
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Unit B.indd 34
Block B
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How do the additions we have been working on help with this board?
We are trying to find complements to 1000, pairs of numbers that sum
to 1000.
After discussion establish that, as before the bonds to 10 help with the
related bond when adding multiples of 100, e.g. 9 + 1 and 900 + 100.
Highlight, or ask a child to highlight, bonds as they are identified.
Groups/pairs/individuals
Core
RS B4
Children find pairs of numbers
that sum to 1000. They use
these to find the total of all of
Link complements to 1000 involving
fifties, to the earlier work with
numbers involving fives, e.g. 350 + 750.
the numbers on the board.
Use Start again to refresh the board.
Children find pairs of numbers
With your partner find as many pairs as
you can that sum to 1000. Record them
on your whiteboard.
to find the total of all of the
After a few minutes take feedback.
Invite volunteers to click on some
selected pairs and Check each time to
confirm.
RS B6
Support
RS B5
that sum to 100. They use these
numbers on the board.
Extension
Children find pairs of numbers that
sum to 1000. They use these to find
the total of all of the numbers on the
board. Not all pairs sum to 1000.
What to do next
Introduce children to their resource sheets. They can then work on
finding pairs of numbers that sum to 100 or 1000.
Review
Use Settings to return to the set-up screen. Select 4 columns, 4 rows.
Click on Pre-sets and then select Complements to 100, Multiples of 5.
Make board.
What is the total of all of the numbers on this board? How do you
know?
Give children a few minutes to discuss this in pairs. Take feedback. Invite
volunteers to highlight complements to100. Finally establish that there
are eight pairs that total 100. This gives a grand total of 800.
What would the total be if I selected a 6 3 4 board? Take feedback to
confirm there would be 24 tiles making 12 pairs with a total of 100. The
grand total would therefore be 1200.
Unit B.indd 35
Block B
ASSESSMENT AfL
Check children can …
• Solve one- and two-step
problems using related number
bonds.
• Describe and explain their
calculation methods.
• Use their knowledge of addition
and subtraction facts and place
value to derive sums of pairs of
multiples of 5, 10 and 100.
• Begin to generalise from the
relationships explored.
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