Least Common Multiple

To find least common multiple you can use one of two methods (unless we specifically want you to find it by a certain method):

Method 1 - the listing method
1. List out the multiples of each number and find the smallest common multiple between the two.

Ex. Find the LCM of 20 and 24
20 - 20, 40, 60, 80, 100, 120, 140, ...
24 - 24, 48, 72, 96, 120, 144 ...

You will notice the LCM is 120 because it is the smallest common multiple

Method 2 - the prime factorization method

Find the LCM of 20 and 24 using prime factorization:
1. Make a factor tree for both 20 and 24
2. Multiply the highest power of each factor.

Ex. 20 = 2 * 2 * 5 or 2 to the second power times 5
24 = 2 * 2 * 2 * 3 or 2 to the second power times 3

So the LCM would be:
LCM = 2 to the third power times 3 times 5 or:
8 (2 to the 3rd power) * 3 * 5 = 120

Adding and Subtracting Decimals

To add and subtract decimals simply line up the numbers by the decimal point, add zeroes if necessary and complete your regular adding and subtracting.

Ex.

22.567 + 3.4 becomes:

22.567
+3.400
25.967

Converting Decimals to Fractions

To convert decimals to fractions look to the place value of the last number in the decimal. Make this place value your denominator. Make the decimal number your numerator.

Ex. 0.166 becomes 166/1000 because the last 6 is in the thousandths place and the decimal is 0.166 so 166 becomes your numerator. We can then convert this to a fraction in lowest terms if we desire.

Converting Fractions to Decimals

To convert fractions to decimals simply divide the numerator (top number) by the denominator (bottom number) using long division.

Ex. To convert 1/8 to a decimal, divide 1 by 8 to get 0.125