Help With Multiplication and Percents
Date: 11/11/96 at 19:24:42 From: Amanda Oakley Subject: Math Dear Dr. Math, I am in grade five and have lots of trouble! My class is a mix of fifth and sixth graders so we are doing percentages, which are really hard for me because I am not very good at multiplication and anything else in that area. Can you please help me? Sincerely, Amanda Oakley
Date: 11/23/96 at 15:44:27 From: Doctor Lim Subject: Re: Math Dear Amanda, Don't worry so much. If you put time and effort towards your study of mathematics, soon you will see results. You are already taking a good first step by figuring out what areas are hard for you, like multiplication. If this is the root of your troubles, I can try to help you fix it. There is no easy way to learn multiplication. If you understand the concept of multiplication, the only way to improve your skills is to practice what you have learned. Most of the time problems seem difficult only because they look big and scary. Problems became less frightening when you break them up and see them as little pieces. You do not eat a whole cake up in one mouthful, do you? You have to bite it into pieces or cut it up into slices before eating it, right? So if you learn your multiplication tables, everything else will fall into place. My students find learning nine times tables to be the hardest. After using this method it becomes easier for them: Put your hands flat, palms down, on the table. Number your fingers like this: Left Hand Right Hand 1 2 3 4 5 6 7 8 9 0 If you have difficulty remembering this, try writing the numbers on the backs of your hands. Think of a number to multiply by 9. Let's try 7 x 9: Tuck your 7th finger underneath your palm. You should have 6 fingers open to the left of your hidden finger and 3 fingers open to the right of it. 7 x 9 = 63 Now try it out with 4 x 9: Tuck your 4th finger underneath your palm. You should have 3 fingers open to the left of your hidden finger and 6 fingers open to the right of it. 4 x 9 = 36 Got it ? For the rest of the multiplication tables, try looking at this site, which teaches multiplication tables as a song: http://www.schoolhouserock.com/multrock/ The key to finding percents is to recognize that a percent is just a different way of writing a decimal. Let us start with an example. Suppose we are given a group of 100 people, 70 of whom are men and 30 of whom are women. This means that 70 out of 100 or 70/100 of the group are men. There are lots of different ways to write 70 out of 100: 70/100 0.70 70 per cent 70% 70% of the people are men Let us look at another example. Suppose that in my library there are 100 books, 40 of which are big and 60 of which are small. There are lots of different ways to write 40 out of 100: 40/100 0.40 40 per cent 40% 40% of my library books are big books. The notion of percent is very closely related to fractions, which you can see by noticing that 40 out of 100 means: 40/100 = 4/10 = 2/5 = 0.40 = 40% Math is just like a big family. All of its parts are related to each other. If you can understand one part, the other parts are not that difficult. Please get back to me if you have problems. -Doctor Lim, The Math Forum Check out our web site! http://mathforum.org/dr.math
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