Chanhee's Math Blog

News Letter 1

chanheeh — Wed, 03 Dec 2008 08:20:55 +0000

Here is My first News Letter using LetterPop.

Two Types of Quadratic Formula

chanheeh — Tue, 02 Dec 2008 07:52:28 +0000

When I was a high school student in Korea, I learned two types of quadratic formula.

If the quadratic equation is in the form of .

As you know, the first quadratic formula is the famous .

We learned one more thing. The other one is used only if b is a even number.

If we let b be 2d in the quadratic equation, it will be , right?

Then, the new quadratic formula becomes .

You already figured out how I got the second one!!

If we substitute 2d into b in the original quadratic formula,

we could get ,

which is and we can just reduce them.

And finally got the new quadratic formula ,

when the quadratic equation is .

Do you know why we used two types of quadratic formula in Korea? We had to solve all the math problems mentally without any calculator in a short time. Believe or not, the second quadratic formula sometimes helped me a lot to save time!

You can try it now.

Solve using the second type of quadratic formula

(Hint: in this case, d becomes 12/2, which is 6)

2008-09 SAT Test Dates and Registration Deadlines

chanheeh — Sat, 29 Nov 2008 11:05:06 +0000

Test Dates / Regular Registration Deadlines / Late Registration Deadlines

- October 4, 2008/ September 9, 2008/ September 16, 2008(by mail),19(online or by phone)
- November 1, 2008/ September 26, 2008/ October 10, 2008
- December 6, 2008/ November 5, 2008/ November 18, 2008(by mail),19(online or by phone)
- January 24, 2009/ December 26, 2008/ January 6, 2009 (by mail), 9(online or by phone)
- March 14, 2009/ February 10, 2009/ February 24, 2009
- May 2, 2009/ March 31, 2009/ April 9, 2009 (by mail), 14(online or by phone)
- June 6, 2009/ May 5, 2009/ May 15, 2009 (by mail), 19(online or by phone)

Symbolic Representation

chanheeh — Sun, 23 Nov 2008 07:00:21 +0000

You can translate the math problems into an algebraic equation. Translating words into symbols can be a very helpful problem solving skill the symbols stand for numbers that vary or remain constant.

Three friends went to the gym to work out. None of the friend would tell how much he or she could leg-press, but each hinted at their friends’ leg-press amount. Chen said that Juanita and Lou averaged 87 pounds. Juanita said that Chen leg-pressed 6 pounds more than Lou. Lou said that eight times Juanita’s amount equals seven times Chen’s amount. Find how much each friend could leg-press.

Let C, J and L represents Chen, Juanita, and Lou’s leg-press weight in lbs respectively.

We can express the problems as equations in terms of C, J and L.

Can you do this?

LCM and GCF

chanheeh — Thu, 13 Nov 2008 08:14:15 +0000

The least common multiple (LCM) of two numbers is the smallest number that is a multiple of both of the numbers. The greatest common factor (GCF) of two numbers is the greatest number that is a factor of both numbers. For example, LCM of 36 and 56 is 504 and GCF of 36 and 56 is 4.

We can find LCM and GCF very easily through prime factoring.

2 | 36 56

2 | 18 28

9 14

You have to stop at this point because there is no number that can divide both 9 and 14. And then 2*2 becomes the GCF of 36 and 56 and 2*2*9*14 is the LCM of two numbers.

Solve some practice problems.

1. Find the LCM and GCF of 64 and 120.

2. Find the LCM and GCF of 294 and 315.

Ratio

chanheeh — Thu, 13 Nov 2008 07:04:37 +0000

A ratio is a comparison of two numbers. We generally separate the two numbers in the ratio with a colon (:). Suppose we want to write the ratio of 8 and 12. We can write this as 8:12 or as a fraction 8/12, and we say the ratio is eight to twelve. When we want to find out the ratio of A to B is equal to the ratio of C to D, we can express it like A:B = C:D?

And then you check inner product is equal to outer product, which is A*C = B*C.

If the satement is true, the ratio of A to B is equal to the ratio of C to D.

Solve the problem

1. Are the ratios 7:1 and 4:81 equal?

2. Solve for n. 1:2 = n:4.

3. In a map, 2 inches represent 5 miles in a real distance. How far does 6 inches in the map represent?

How to calculate Percentage.

chanheeh — Thu, 13 Nov 2008 06:48:42 +0000

Percentage means part of 100.

If you say A %, it means A/100 in real number.

When you say A percent of B is C, it can be expressed as (A/100)*B = C.

It is the same statement as A = (C*100)/B or B=(C*100)/A.

Solve the sample problem.

1. Calculate the 25% of 800

2. 25% of a certain number is 200. Find the number.

3. What percent of 800 is 200?

You can solve all the problems with the same equation.

Welcome to Chanhee’s Blog!

chanheeh — Fri, 07 Nov 2008 03:35:26 +0000

Welcome to chanhee’s Math Blog. I want to share anything about math with you in my blog.