Subtracting Whole Numbers
Subtraction of whole numbers is used by everyone. For example, to find the sale price of an item, a store clerk subtracts the discount from the regular price. To measure climate change, a scientist subtracts the high and low temperatures. A trucker subtracts odometer readings to calculate the number of miles driven on a trip.
To subtract two whole numbers, think of taking away objects from a set. For example, if we start with a set of 9 stars and take away a set of 4 stars, a set of 5 stars is left.
If the subtraction of the digits in any place value column requires that we subtract a larger digit from a smaller digit, we must borrow or regroup
To describe the special relationship between addition and subtraction, we say that they are inverse operations