Prime Numbers: Prime Factorizations
This clip explains that when the factorization of a whole number consists entirely of prime numbers (as with the number thirty, factored into two times three times five), the result is what's known as a prime factorizati..
Prime Numbers: Prime and Composite Numbers
This clip explains the difference between prime numbers and composite numbers. It also talks about how the Greeks figured out which numbers are primes and which are not.
Prime Numbers: Summary: Prime Numbers
This clip summarizes prime numbers, explaining the difference between prime and composite numbers, and demonstrating how to use the sieve of Eratosthenes to find prime numbers. The clip also explains prime factorization,..
Ratio and Proportion: Defining Ratio and Proportion
This clip provides definitions and example of the words "ratio" and "proportion." The clip explains that we will be using the word ratio " as a way of describing the relative sizes of two numbers." The clip also says th..
Ratio and Proportion: Knowing Whether Two Fractions Are Equal
This clip explains that the way to find out whether two fractions are equal is to write them with a common denominator. If the numerators are equal, the fractions will be equal.
Ratio and Proportion: Practical Problem: French Toast, A
This clip presents a problem involving cooking ingredients needed to make French toast. As in other proportion problems, we are given three pieces of information and have to find the fourth. The problem is solved through..
Ratio and Proportion: Problem In Which The Denominator Is Missing, A
This clip explains that, whether it's a numerator or a denominator that's missing, in order to be sure that " we really have a proportion...the cross products must be equal."
Ratio and Proportion: Proportions In the Use of Map Scales
This clip presents a problem involving the scale on a road map comparing inches to miles. The clip explains that checking the answer to see that it makes sense is especially important in proportion problems, because " w..
Ratio and Proportion: Simplifying the Comparing of Fractions by Cross Multiplying
This clip explains that cross multiplying is a shortcut which allows us to determine if two fractions are the same. The fractions are compared by multiplying the numerator of each by the denominator of the other. If the ..
Ratio and Proportion: Solving Word Problems Involving Proportions
This clip presents two word problems involving proportions which require dividing both sides of an equation by the same number. The answers are checked by forming cross products which are equal.