Video Transcript
Making Eight and Nine
In this video, we will learn how to
use models and addition equations to show all the different ways to make eight and
nine. We could use cubes to help us find
all the ways to make eight. We can see from the model that we
can make eight using one red cube plus seven blue cubes. One and seven is eight. We could also make eight using two
red cubes and six blue cubes. One plus seven is eight. Two plus six is eight.
Can you predict what the next
number bond would be? In the first number bond, we had
one red cube. In the second, we had two. We’re increasing the number of red
cubes by one each time, one, two, three. We can make eight using three red
cubes, but how many blue cubes? The number of blue cubes is
decreasing by one each time. We’re taking away one blue cube
each time, seven, six, five. So far, we found three different
ways to make eight: one plus seven, two plus six, and three plus five.
It helps to use a strategy to find
all the possible ways of making a number. We started with one red brick. We added one red brick each time
and took away one blue brick each time. This helped us to find all the
possible ways of making eight. We didn’t find all the possible
ways of making eight. We’re going to do that with some
practice questions.
We call the pairs of numbers which
make nine number bonds to nine. Seven and two makes nine. Seven blue bricks and two red
bricks is nine. We didn’t record all the ways of
making nine or use a strategy. Let’s practise, finding all the
ways to make eight and nine using models and addition equations.
There are lots of ways to make
eight. What is the missing
expression? Zero plus eight. One plus seven. Two plus six. What plus what. Four plus four. Five plus three. Six plus two. Seven plus one. And eight plus zero.
There are nine ways to make
eight, but one of the expressions is missing. We could use the cube train to
help us find the missing expression. We could also find the missing
expression by working out the strategy that’s been used. If we look carefully at the
pairs of numbers or the number bonds, we can spot some patterns.
If we write down the number of
red bricks and blue bricks we’ve used to make eight, that will help us to spot
the pattern. What’s happening to the number
of red bricks? Zero, one, two, three, four,
five, six, seven, eight. The number of red bricks is
going up by one each time. We’re counting in ones. Now we found the first missing
number. Zero, one, two, three.
What’s happening to the number
of blue bricks? Eight, seven, six. The missing number is five. Eight, seven, six, five, four,
three, two, one, zero. The number of blue bricks is
getting smaller each time; it’s decreasing. We’re counting back in ones,
eight, seven, six, five. The missing expression is three
plus five. Zero and eight make five, one
and seven, two and six, and three and five. So do four plus four, five plus
three, six plus two, seven plus one, and eight plus zero.
We found all the ways to make
eight using our model and a strategy. We wrote the number bonds down
and looked for the pattern. This helped us to find the
missing addition expression. Three plus five makes
eight.
Find the missing addition
sentence. Nine plus zero is nine. Eight plus one is nine. Seven plus two is nine. Six plus three is nine. Five plus four is nine. What plus what is nine. Three plus six is nine. Two plus seven is nine. And one plus eight is nine.
The model shows all the number
bonds to nine. The pictures use blue and green
tennis balls to model the addition expressions. Let’s look more closely at the
strategy that’s been used to find the pairs. In other words, let’s look
closely at the numbers in the number bonds. Let’s see if we can spot any
patterns.
Nine blue tennis balls and no
green tennis balls makes nine. Eight and one is nine. Seven and two is nine. Six and three is nine. Five plus four is nine. Have you spotted the pattern
yet? Did you notice what’s happening
to the number of blue balls each time? Nine, eight, seven, six,
five. The numbers are decreasing. The number of blue balls is
going down. There’s one less blue ball each
time. Which number would come
next? Nine, eight, seven, six, five,
four.
Now we need to work out the
number of green balls. Let’s see if we can spot the
pattern. Zero, one, two, three, four,
five. The number of green balls
increases by one each time. We’re adding one green ball
each time. The missing addition sentence
is four plus five is nine.
We found the missing addition
sentence by looking closely at what happened to the number of blue and green
balls each time. We could use the model to help
us check the answer. Are there four blue balls? One, two, three, four. Yes, there are. Let’s check there are five
green balls. One, two, three, four,
five. Four plus five is nine.
Think about making eight. Find the missing numbers. What plus one equals eight. Three plus what equals
eight.
We’re given two addition
expressions which make eight. Something plus one equals eight
and something plus three equals eight. What do we add to one to make
eight? To find the answer, we could
count the number of squares. One, two, three, four, five,
six, seven. Seven plus one equals
eight.
Let’s find the missing number
in the second pair of numbers. Three and what makes eight. Three and one, two, three,
four, five makes eight. Seven add one equals eight. Three add five equals
eight. The missing numbers are seven
and five. We used part-whole models and
bar models to help us find the missing numbers.
What number is missing? Nine is five and what more.
Let’s use a part-whole model to
help. We know that the two groups of
counters make nine. We know that five blue counters
and a number of orange counters total nine. How many orange counters are
there? One, two, three, four. Nine is five and four more. We used the number of counters
and a part-part-whole model to help us find the missing number. Nine is five and four more.
What have we learned in this
video? We’ve learned how to use models and
addition equations to show all the ways to make eight and nine.
