How do make 21

Question

Ways to make 21 is 20+1=21 or 1+20=21

Answer 1

The title is not a good one. There are infinitely many pairs of numbers that add up to exactly 21, e.g. 26 + (-5).

Of course, the order of adding two quantities is irrelevant, as Mark points out.

 

In this connection, you should also learn the method of dealing with sums in which the signs of the two quantities differ; said rule involves subtraction of the smaller absolute value from the larger absolute value, and then affixing the proper original sign of the original number having the larger absolute value.

 

This can be played out on the number-line, as I am sure you are being shown in your math class. Pay close attention, and ask questions whenever necessary to come away with total understanding.

Answer 2

Either way, It is a demonstration of the Commutative Property of Addition (Learn it!).