Now I know a lot of 3/4J are mathematicians, but did you know

they are also matheMAGICIANS!

 

This week we practised how to add and subtract numbers without counting.

Using our knowledge of place value and number relationships we were able to quickly work out the missing numbers in number sentences such as

 

20 – 7 = _____

15 + _____ = 20

30 – 12 = _____

30 – _____ = 27

 

When we look at 20 – 7, we see know that 20 s made up of 2 tens. We can see that we are not subtracting a number greater than ten, so one of the tens will remain in the answer.

 

S0 20 – 7 = 10 + ____

The number that goes with the ten matches 7 in a ten pair. SEVEN and THREE are ten pairs.

 

So 20 – 7 = 10 + 3

20 – 7 = 13!

When some people in 3/4J became Mathemagicians they could answer 10 subtraction questions in UNDER 30 SECONDS!

See, magic!

So make sure you know your place value and number relationships like the friends of 10!

Play some PLACE VALUE games here!