Posted by: cyncas | February 19, 2010

Adding 10

This week, during our Math sessions, we continued expanding working with 10.  First we counted in 10’s, then found out that when we add 10 we change the first digit only as that represents the tens.  We found out that when a number is on its own – a unit – and we add one 10, then we just put a 1 in front of that digit.  When our number has two digits, we need to look at the first number and see how many 10’s we are going to add to it.  It was a bit tricky to understand the full concept, but then we realized it was really easy and quicker than if we had to count on our fingers. 

‘Remember:  look at the first digit – that is the tens that we need to change.  Now look at how many tens you are going to add – the first number shows you how many tens…..  Take the first digit of the first number and add with it the number of tens and write that down.  Since we are adding whole tens, the second digit does not change’.  Example:  8+10= (8 is a unit and we are going to add 1 ten to it therefore we put a 1 in front of the 8)=18, 15+10+(the 1 on the 15 shows us we have 1 ten to which we need to add another 1 ten, therefore 1+1 makes 2 then you need to write 25 since we are not changing the last digit)+25…  Try a few practices at home and you can turn it into a game.


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