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
Monday, November 2, 2009
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
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.
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
Ex. To convert 1/8 to a decimal, divide 1 by 8 to get 0.125
Thursday, October 29, 2009
Greatest Common Factor
Greatest Common Factor (GCF) - the greatest common factor of two or more numbers is the largest factor they have in common.
To find the GCF of two numbers you can either use:
1. the listing method
2. the prime factorization method
The listing method:
list out the factors of each number and take the largest factor that they both share.
The prime factorization method:
Complete the prime factorization for each number. Multiply the pairs of prime factors that they both share together. Discard the prime factors that they do not both share. The product of the pairs of prime factors that they both share is the GCF.
To find the GCF of two numbers you can either use:
1. the listing method
2. the prime factorization method
The listing method:
list out the factors of each number and take the largest factor that they both share.
The prime factorization method:
Complete the prime factorization for each number. Multiply the pairs of prime factors that they both share together. Discard the prime factors that they do not both share. The product of the pairs of prime factors that they both share is the GCF.
equivalent fractions
Equivalent fractions: two fractions are said to be equivalent if they represent the same quantity.
To make fractions equivalent divide or multiply both the numerator (top number) and denominator (bottom number) of a fraction by a convenient number.
When dividing a convenient number is a number that goes both into the numerator and the denominator.
When multiplying a convenient number is a whole number greater than 1.
To make fractions equivalent divide or multiply both the numerator (top number) and denominator (bottom number) of a fraction by a convenient number.
When dividing a convenient number is a number that goes both into the numerator and the denominator.
When multiplying a convenient number is a whole number greater than 1.
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