<p>hi all, with jan sat only one day away I was getting stuck on a math problem in the blue book in test one. (The official SAT study guide second edition). The problem is in section seven question 17. How is the answer 90?</p>
<p>I will give you a hint first. </p>
<p>What kind of a triangle is the little dashed triangle with one of the sides labeled as DE? Do we know the lengths of the dashed line segments?</p>
<p>I know that the triangle is an equilateral triangle but how do we know the length of the overlap?</p>
<p>Ok, we are given that CD=DE=EF=10. And the little dashed triangle is also equilateral triangle with all three sides equal to 10. </p>
<p>If we assign X to be the vertex of the dashed little triangle, then the perimeter of the bold figure = AF + EF + DE + DC + BC + BX + AX </p>
<p>here CE = DE + CD = 10 + 10 = 20 is the side of the equilateral triangle BEC, this is also the same for the other equilateral triangle. </p>
<p>Therefore, AF = 20, EF = 10, DE = 10, DC = 10, BC = 20. </p>
<p>We are left with BX and AX, they are both equal. </p>
<p>and BX = BE - XE = 20-10 = 10 </p>
<p>Therefore, the perimeter = 20+10+10+10+20+10+10=90</p>
<p>If this is still not clear(it is hard to explain without a figure), watch the video explanation at this link:
[PRACTICE</a> TEST 1 SECTION 7 QUESTION 17 MATH OFFICIAL SAT STUDYGUIDE - OG1Journal - satquantum](<a href=“http://www.satquantum.com/og1journal/2012/1/18/practice-test-1-section-7-question-17-math-official-sat-stud.html]PRACTICE”>http://www.satquantum.com/og1journal/2012/1/18/practice-test-1-section-7-question-17-math-official-sat-stud.html)</p>