Today's focus is subtraction. We are going to count backward using our tens and ones knowledge. We use a number square or a number line.
Starter: Count on and back from 2 and 3-digit numbers, clapping each count and double-clapping to change direction.
We are going to complete this task together. 76 - 35 =? So what do we know are 35. It is made of 3 tens (30) and 5 ones (5). So we can jump backwards in tens first. 76, 66, 56, 46. Then jump back five. 46, 45, 44, 43, 42, 41. So our answer is 41. Lets do a quick inverse to check our answer. 35 + 41 = 76. You could use the number square resource if you are lucky enough to have a printer.
Another way is to count forwards on a number line. This is always a tricky way and some just can't see the method, so keep practising it will become clear.
First write the number sentence our 76 - 35 =
Then draw a line and write 35 at one end then 76 at the other.
Then jump to the next multiple of ten from 35, which will be 40. write the number above (5). Then jump in tens to 70 or a big jump to 70 if you are more confident (30). Then finally to 76 (6). Then you will need to add your jumps together. 30 + 5 + 6 = 41.
See the picture below.
Now we have talked through this, using your number cards or a dice to create two 2-digit numbers. Have a go at talking through how to work out the answer, using all the methods above. The number line is definitely the trickiest and causes some confusion, but keep practising and growing that brain. Remember we always take the smallest number from the biggest number; to talk through your answers using that language of tens and ones. Explain how the number is made up e.g. 86 is made of 8 tens and 6 ones. I know that 35 is smaller than 86 so I will take 35 from 86. There are 3 tens and 5 five ones in 35 etc....
This can even be taken outside on your daily walk. Look for numbers around you, pick two and then talk through, as above, how to work out the answer. Great Mental Maths on the go!