This math problem perplexes me www.imageurlhost .com /images/7z0u82jv5og7znwu5.jpg:
“On end of an 80 inch long paper strip is shown in the figure above. The notched edge, shown in bold, was formed by removing an equilateral triangle from the end of each 4-inch length of one edge of the paper strip. What is the total length, in inches, of the bold notched edge on the 80-inch paper strip?”
What I did was that I counted the three 3s then, since it said the triangle was equilateral, I counted only two out of the three sides of the triangle since the two were bolded while the bottom straight one wasn’t. So, three 3s plus three 2s = 9+6 = 15.
So why isn’t the length just 15 in???
They don’t just want the length of the portion of the bold line shown in the diagram. They want the entire length that would fit along the 80-inch strip of paper!
So look at each 5 inch section…notice that it takes up 4 inches of length along the strip. And the strip is 80 inches long, so there will be 20 of those 5-icn sections, which adds up to a total length of 100 inches.
Also, as a way to have caught your error, notice that the way you did it never made use of the fact that the strip is 80 inches long. For most (not all, but most) SAT problems, every bit of given info is important. So if you are not using some of the info, proceed with caution. I’m not saying that you will ALWAYS need every bit of info, but that is certainly true of more than 90% of SAT problems.