Proportions

Link of the Day

Using current events in your SAT essay will impress your readers with the idea that you are informed about the world around you.  However, you are not limited to current events on this planet.  For example, have you heard the whimsical story about the Mars rover taking pictures of itself?  If not, follow this link to read the article.  This is a cute story, but it also relates to science, planning, creativity, and even self-awareness – topics that have shown up on the SAT.   With just a little more research, you could use the Mars rover as one of your excellent examples for the essay.  

9/9 Proportions

Read the following SAT test question and then select the correct answer.

Read the question carefully to glean as much information as possible.  Then identify your bottom line, assess your options for solving the problem, and attack that question in the most efficient way possible.  When you have found an answer, loop back to make sure that you have answered the bottom line.

A group of workers can harvest all the grapes from 10 square meters of a vineyard in ½ minute. At this rate, how many minutes will the group need to harvest all the grapes from100 square meters of this vineyard?

Did you make a note of the bottom line?  The bottom line is the number of minutes it takes to harvest 100 square meters.  There are a number of ways to think about this problem, but one of the easiest ways is to set up a proportion.  You could set it up as time over area.  Write the ½ as .5 just so that you do not get confused between the fraction and the proportion.



When you set up the problem like this, you can easily see that in the denominator you would need to multiply the first 10 by 10 to get the second denominator of 100.  Anything you do to the bottom of a fraction you must also do to the top.  Multiply the .5 by 10 and you will get 5.  You solved for minutes just as the question asked you to do.  Look down at your answer choices.

(A) 5
(B) 10
(C) 20
(D) 50
(E) 60

The correct answer is (A).


On sat.collegeboard.org, 69% of the responses were correct.

For more help with the math section of the SAT, visit www.myknowsys.com!