{"id":6605,"date":"2019-08-13T10:08:07","date_gmt":"2019-08-13T15:08:07","guid":{"rendered":"http:\/\/www.kaptest.com\/blog\/business-school-insider\/?p=6605"},"modified":"2020-09-11T20:41:26","modified_gmt":"2020-09-11T20:41:26","slug":"geometry-problem-shortcuts","status":"publish","type":"post","link":"https:\/\/wpapp.kaptest.com\/study\/gmat\/geometry-problem-shortcuts\/","title":{"rendered":"GMAT Geometry Problem Shortcuts"},"content":{"rendered":"

GMAT geometry problems tend to be one of the scariest of the Quantitative topic areas. Fortunately, all the geometry you need to remember could fit in the palm of your hand. Since you can\u2019t actually put it in your palm on Test Day, here are some tricks for tackling GMAT geometry without notes.
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Geometry problems with lines and angles<\/h4>
<\/div><\/div><\/div>
\n\u00a0\"geom1\"<\/a><\/strong><\/strong>
\nIf you are given a figure such as this, with no angle measures provided, all you would know is that certain pairs of angles sum to 180<\/strong><\/span>\u00b0<\/strong> and the sum of all four angles is 360<\/strong><\/span>\u00b0<\/strong>.<\/span>
\nThere is no way to determine the measures of individual angles, <\/span>so answer choices other than 180\u00b0 or 360\u00b0 will not be correct.<\/span>
\n

Finding the area of triangles<\/h4>
<\/div><\/div><\/div>
\nThe formula for the area of a triangle<\/b> is \"Screen<\/a><\/span>
\nA triangle\u2019s base and height must be\u00a0perpendicular (meeting at a 90-degree angle). Right triangles are the only type of triangle that have side lengths as base and height. For all other triangles, consider one side the base and then draw in a line for the height.<\/span>
\n\u00a0\"geom2\"<\/a><\/strong><\/strong>
\nEquilateral<\/b> triangles have equal side lengths and angle measures; because all triangles have an internal angle sum of 180\u00b0<\/strong>, each angle in an equilateral triangle is 60\u00b0<\/strong>.<\/span>
\nIsosceles<\/b> triangles have two equal sides, and they also have two equal angles. Any time the GMAT presents a triangle with one vertex at the center of a circle, the triangle will be isosceles as each side will be the radius of the circle.<\/span>
\n\"geom3\"<\/a>
\n

Quadrilateral figures<\/h4>
<\/div><\/div><\/div>
\nThe formula for the area of a <\/span>quadrilateral<\/b> (four-sided figure) is <\/span>(base)(height)<\/span>. <\/span><\/em>
\nBase and height must also be perpendicular for polygons other than triangles. In a rectangle, all angles are 90\u00b0<\/strong>, but in a <\/span>parallelogram<\/b> (a figure with two pairs of parallel sides) that is not a rectangle, you must draw the height just like with a triangle.<\/span>
\n\"geom4\"<\/a>
\nRectangles and squares are types of parallelograms, ones where all the angles are equal.
\n

Formulas for circles<\/h4>
<\/div><\/div><\/div>
\nThe formula for the area of a circle<\/b> is\u00a0\"Screen<\/a>\u00a0<\/span>and the formula for the <\/span>circumference<\/b> is \"Screen<\/a>.<\/span>
\nSome people have trouble keeping the two important equations straight when they encounter a circle geometry problem on the GMAT, so here is a mnemonic to help you remember:<\/span>
\n\"Screen<\/a><\/span>
\n\u00a0\u00a0\"Screen\u00a0\u00a0<\/span>
\nYou have to raise your voice an octave or so when you say \u201ctoo\u201d at the end, to remember that the 2 is an exponent. Give it a try<\/span>
\n

Circle component ratios<\/h4>
<\/div><\/div><\/div><\/p>\n
\n
\nCircles found in the Quantitative Reasoning section are often drawn with a\u00a0central angle<\/b>\u00a0marked; in the figure below, the central angle is X. Angle X measures\u00a0n<\/i>\u00b0. Points A and B along the circle\u2019s circumference represent the\u00a0arc<\/b>. Imagine that this circle is a pizza and the shaded area represents one slice. The arc is the crust on one slice of the pizza. The slice itself, bordered by the arc and the central angle, is called a\u00a0sector<\/b>.
\n\"image01\"<\/a><\/strong><\/strong>
\nThe measure of the central angle represents a fraction of the measure of the whole circle (360\u00b0), and the length of the associated arc represents the same fraction of the circumference (2\u03c0r). The area of the sector is also the same fraction of the area of the circle (\u03c0r\u00b2).
\nLooking at the circle above, let\u2019s say\u00a0n<\/i>=60\u00b0. What fraction of the entire circle is that?
\nThis central angle is \u2159 of the circle. Using the pizza analogy, if a pizza is cut into 60\u00b0 slices, it is cut into 6 slices. The area of one slice is \u2159 of the area of the entire pizza. Its arc represents \u2159 of the circumference of the pizza, or \u2159 of the crust.
\nThese three fractions can be written as follows:
\n\"image03\"<\/a>
\nTogether, they form the circle ratio that you need to know for some of the GMAT\u2019s geometry problems.
\nNow let\u2019s go back to our circle above and take it further. Let\u2019s say the diameter of the circle is 12. That means the radius is 6, the circumference is 12\u03c0, and the area of the circle is 36\u03c0. We can use these values to solve for the arc length by plugging the numbers into the ratio:
\n\"image04\"<\/a>
\nSolving for arc length by cross-multiplying and dividing, we find arc = 2\u03c0. We can then do the same thing to find the area of the sector:
\n\"image05\"<\/a>
\nSolving for the sector area by cross-multiplying and dividing, we find sector = 6\u03c0.
\n

Finding the volume of a solid<\/h4>
<\/div><\/div><\/div>
\nThe formula for the <\/span>volume<\/b> of a <\/span>rectangular solid<\/b>, such as a cube, is\u00a0\"Screen<\/a><\/span>\u00a0For a <\/span>cylinder<\/b>, it\u2019s\u00a0\"Screen<\/a><\/span>
\nInstead of memorizing those formulas, all you really need to do is remember this one: for any solid on the GMAT,\u00a0<\/span>v=(area of base)<\/span>(height)<\/span><\/em>. The base of a rectangular solid is a rectangle, and the area can be found using \"Screen<\/a><\/span>\u00a0Multiply that by the height and you have \"Screen<\/a><\/span>
\nFor a cylinder, the base is a circle with area \"Screen<\/a><\/span>. To find the volume, multiply that area times the height, or \"Screen<\/a><\/span>\u00a0Using your critical thinking skills while reviewing content during your prep can be as important as using it while answering questions!<\/span>
\n

Coordinate geometry problems<\/h4>
<\/div><\/div><\/div>
\nEvery line on a coordinate system can be expressed in the form\u00a0y<\/em> =\u00a0mx<\/em> +\u00a0b<\/em><\/strong> where\u00a0m<\/em> is the slope and\u00a0b<\/em> is the y<\/em>-intercept (that is, the point where the line crosses the\u00a0x<\/em> axis).
\nBe sure you are comfortable with the relationships between parallel and perpendicular lines in the coordinate plane. Lines that are <\/span>parallel <\/b>have the same slope; they continue at the same slope to infinity and never cross. A line that is <\/span>perpendicular<\/strong> to another line has a slope that is the negative<\/span>\u00a0reciprocal (change the sign and flip the fraction) of the other line\u2019s slope.<\/span>
\nFor example, <\/span>y\u00a0<\/em>=\u00a023x\u00a0<\/em>+ 4 will be parallel to all other lines that share a slope of <\/span>2<\/span>3<\/span>. A line that is perpendicular to <\/span>y\u00a0<\/em>=\u00a023x\u00a0<\/em>+ 4 would have a slope of \u00a0-(1\/23)<\/span>, which you find by changing the positive sign to a negative and taking the reciprocal of the fraction.<\/span>\n<\/div>\n<\/div>\n

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Jennifer Mathews Land has taught for Kaplan since 2009. She prepares students to take the GMAT, GRE, ACT, and SAT and was named Kaplan\u2019s Alabama-Mississippi Teacher of the Year in 2010. Prior to joining Kaplan, she worked as a grad assistant in a university archives, a copy editor for medical web sites, and a dancing dinosaur at children’s parties. Jennifer holds a PhD and a master\u2019s in library and information studies (MLIS) from the University of Alabama, and an AB in English from Wellesley College. When she isn\u2019t teaching, she enjoys watching Alabama football and herding cats.<\/p>\n<\/div><\/div>

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Jennifer Land<\/strong><\/div><\/div><\/div><\/div>\n<\/section><\/div><\/p>\n

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GMAT geometry problems tend to be one of the scariest of the Quantitative topic areas. Fortunately, all the geometry you need to remember could fit in the palm of your hand. Since you can\u2019t actually put it in your palm on Test Day, here are some tricks for tackling GMAT geometry without notes.   \u00a0 […]<\/p>\n","protected":false},"author":1,"featured_media":27631,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[55],"tags":[56,80],"_links":{"self":[{"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/posts\/6605"}],"collection":[{"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/comments?post=6605"}],"version-history":[{"count":2,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/posts\/6605\/revisions"}],"predecessor-version":[{"id":34918,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/posts\/6605\/revisions\/34918"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/media\/27631"}],"wp:attachment":[{"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/media?parent=6605"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/categories?post=6605"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpapp.kaptest.com\/study\/wp-json\/wp\/v2\/tags?post=6605"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}