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Sharpen Your Math Skills |
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| www.iselong.com 日期：2006-03-06 10:33
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主题: Sharpen Your Math Skills
Whether you’re thinking of a career as an accountant or just trying to
balance your checkbook, you face math in some way, shape or form every
single day.
Not only are strong math skills important to doing well in school, they are
also critical to your success in everyday life. You have to pay bills; plan
for a financially secure future; pay taxes; and you probably split the
cable bill with your roommate.
A Language All Its Own Think of mathematics as its own language. Just like
the language of words, grammar, and punctuation, the language of math is
precise. It helps to know as much of the rules, vocabulary, and methods as
possible to make informed decisions about problems on a test or in day-to-
day life.
So the main lesson here is to look at the big picture. Look at how
individua l parts of a problem relate to a whole. You’ll gain a better
understanding of the concepts behind the numbers. And in the process, you’
ll gain a better understanding of the world around you.
Practice Questions
Try out the practice problems below and see how you do. Each represents
some important math concepts that are critical to success at school, on the
job, and in life. The answers are below.
1. In May, Gina sold 40 percent more magazine subscriptions than she had in
April. In June, she sold 20 percent more subscriptions than she had in May.
The number of magazine subscriptions Gina sold was what percent greater in
June than in April?
(A) 60
(B) 64
(C) 68
(D) 72
(E) 80
2. Directions: Answer (A) if the quantity in Column A is greater; (B) if
the quantity in Column B is greater; (C) if the two quantities are equal,
or (D) if the relationship cannot be determined from the information given
Square A has sides of length x and square B has sides of twice this length.
Column A
Area of square A
Column B
Half the area of square B
Answers and Explanations
1. The correct answer is (C). Since we are not given a number for how many
subscriptions Gina sold in April, let’s pick a number. Let’s pick 100.
When you have a percent problem and numbers are not provided, you should
always pick 100 because it is easy to work with.
In April, let’s say Gina sold 100 magazines. We are told that in May she
sold 40 percent more magazine subscriptions than she had in April so the
number she sold in May is 100 plus 40 percent of 100, or 140. In June, Gina
sold 20 percent more subscriptions than she did in May. Well, in May she
sold 140 subscriptions and 20 percent of 140 is 20 percent times 140 or 28.
Therefore, in June, Gina sold 140 plus 28 subscriptions, or 168
subscriptions. The percent that the number of magazine subscriptions sold
in June, 168, is greater than the number sold in April, 100, is 68 percent,
answer choice(C).
2. The correct answer is (B). In this question, we are given that one
square, A, has sides of length x and a second square, B, has sides of twice
this length (or 2x), and we are asked to compare the area of A to one half
the are a of B. The first thing you should do is draw a diagram. (You
should draw a diagram when you are not provided with one or when you are
given one that is not drawn to scale.) If you draw the squares somewhat
carefully, the answer becomes obvious.
Figured out mathematically, the area of a square is the side squared.
Column A will, then, yield a square with area x2. Column B will yield a
square with area 4x2. x2 compared to 2x2 gives us an answer choice of (B)
because 2x2 is greater. You could have picked numbers for the sides of the
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