Please enable JavaScript.
Coggle requires JavaScript to display documents.
MENTAL STRATEGIES FOR ADDITION AND SUBTRACTION - Coggle Diagram
MENTAL STRATEGIES FOR ADDITION AND SUBTRACTION
WHAT IS THE ASSOCIATIVE LAW OF ADDITION?
the associative law says that if you have three numbers to add together you get the same answer, whether you start by adding the second and third or start by adding the first and second.
HOW IMPORTANT IS MENTAL CALCULATION?
a reasonable expectation that most children in primary school should be able to learn to add and subtract using informal, mental strategies with three-digit numbers
in mathematics there are many acceptable ways of doing any given calculation and that an effective mental or informal method is as valid as a formal written method.
HOW DOES COUNTING FORWARDS AND BACKWARDS HELP IN MENTAL CALCULATIONS?
these ideas are central to much mental and informal calculation
Confidence in counting backwards and forwards in ones, tens and hundreds is an essential prerequisite for effective mental calculation, so these skills should be taught specifically and reinforced frequently.
HOW DO WE USE MULTIPLES OF 10 AND 100 AS STEPPING STONES?
This process of using a multiple of ten (60) as a stepping stone is an important mental strategy for addition and subtraction.
WHAT IS FRONT-END ADDITION AND SUBTRACTION?
This process is sometimes called partitioning into hundreds, tens and ones.
mentally break the numbers up into hundreds, tens and ones, and then to combine them bit by bit, starting at the front end – that is, starting by adding (or subtracting) the hundreds.
The front-end approach would deal with the hundreds first
WHAT IS COMPENSATION IN ADDITION AND SUBTRACTION?
compensation
You can often convert an addition or subtraction question into an easier question by temporarily adding or subtracting an appropriate small number.
HOW SHOULD THE SYMBOL FOR ‘EQUALS’ BE USED IN RECORDING CALCULATIONS?
encouraged to use the equals sign (=) to link only those things that are actually equal,
children (and some teachers) to abuse the equals sign by employing it rather casually just to link the steps in a calculation,
HOW DO MULTIPLES OF 5 HELP IN MENTAL ADDITIONS AND SUBTRACTIONS?
Multiples of 5 (5, 10, 15, 20, 25, 30, …) are particularly easy to work with. Young children quickly learn to relate simple additions and subtractions to fives.
tendency to relate numbers to multiples of 5 is no doubt related to the way our early experience of counting on our fingers leads us to perceive 6, 7, 8 and 9 as ‘5 and some more’
HOW DO YOU RELATE ADDITIONS AND SUBTRACTIONS TO DOUBLES?
young children will often exploit their facility with doubles to calculate ‘near-doubles’.
HOW ARE MENTAL METHODS USED IN ESTIMATIONS?