Methods used to teach subtraction to elementary school vary from country to country, and within a country, different methods are in fashion at different times. In what is, in the U.S., called traditional mathematics, a specific process is taught to students at the end of the 1st year or during the 2nd year for use with multi-digit whole numbers, and is extended in either the fourth or fifth grade to include decimal representations of fractional numbers.
There are some cases where subtraction as a separate operation becomes problematic. For example, 3 − (−2) (i.e. subtract −2 from 3) is not immediately obvious from either a natural number view or a number line view, because it is not immediately clear what it means to move −2 steps to the left or to take away −2 apples. One solution is to view subtraction as addition of signed numbers. Extra minus signs simply denote additive inversion. Then we have 3 − (−2) = 3 + 2 = 5.
Imagine a line segment of length b with the left end labeled a and the right end labeled c. Starting from a, it takes b steps to the right to reach c. This movement to the right is modeled mathematically by addition:
a + b = c.
From c, it takes b steps to the left to get back to a. This movement to the left is modeled by subtraction:
If the number of inches being subtracted is greater than the number of inches in the length that is being subtracted from, decrease the number of feet by one and increase the number of inches by 12 in the length from which you are subtracting.
Subtract the inches.
Subtract the feet.
Front end estimation mostly produces a closer estimate of sums or differences than the answer produced by adding or subtracting rounded numbers.
How to estimate a sum by front end estimation:
Add the digits of the two highest place values
Insert zeros for the other place values
Example 1: 4496 + 3745 is estimated to be 8100 by front end estimation (i.e. 4400 + 3700).
Example 2: 4496 + 745 is estimated to be 5100 by front end estimation (i.e. 4400 + 700).
An equation is a mathematical statement that has an expression on the left side of the equals sign (=) with the same value as the expression on the right side. An example of an equation is 2 + 2 = 4.
One of the terms in an equation may not be known and needs to be determined. The unknown term may be represented by a letter such as x (e.g. 2 + x = 4). The equation is solved by finding the value of the unknown x that makes the two sides of the equation have the same value.
Find the Least Common Denominator (LCD) of the fractions
Rename the fractions to have the LCD
Add the numerators of the fractions
Simplify the Fraction
