G.GMD.3 STUDENT NOTES WS #4 1 THE PYRAMID The third dimension has a new vocabulary that we need to familiarize ourselves with before we can begin looking at formulas or calculations. A Solid – A three dimensional closed spatial figure. A Polyhedron – a geometric solid with polygons as faces. A Face of a Polyhedron – One of the polygons that form the polyhedron. Sometimes these get called sides but the better term is face. An Edge – The intersection of two faces of a polyhedron. A Vertex – The intersection of two or more edges. To establish the pyramid volume formula we can approach it informally a few different ways. To derive the formula rigorously it requires more mathematics than we have at this level and so here we will simply discuss the informal arguments for this formula. VOLUMEPYRAMID = 1 Bh 3 PYRAMID VOLUME – POURING The classic demonstration is to fill a pyramid with sand or water and then pour that sand or water into a prism that has the same base and height. It is truly a mathematical thing of beauty that exactly three of these fill the prism. From this we informally learn that the volume of a pyramid is 1/3 the volume of prism with the same base and height. PYRAMID CALCULATION The formula for the volume of a pyramid follows directly from the volume of a prism. The pyramid will always be 1/3 the volume of the prism with the same base and height. Example #1 – Square Pyramid 1 Bh 3 1 = ( Base Area)( height ) 3 1 1 = (8)(8) (10) = 213 cm3 3 3 Example #2 – Rectangular Pyramid 1 Bh 3 1 = ( Base Area)( height ) 3 1 = (4)(6) (8) = 64 cm3 3 VPYRAMID Example #3 – Triangular Pyramid 1 Bh 3 1 = ( Base Area)( height ) 3 1 1 = (3)(5) (8) = 20 cm3 3 2 VolumePYRAMID = VolumePYRAMID = VolumePYRAMID = VolumePYRAMID VolumePYRAMID VolumePYRAMID VolumePYRAMID VolumePYRAMID 1 = Bh 3 VolumePYRAMID G.GMD.3 STUDENT NOTES WS #4 2 Sometimes with pyramids and cones the height of the solid is not given and we need to calculate it using the Pythagorean Theorem. In this example we have been given the slant height (l) – the height of the triangular face instead of the height of the pyramid. We are also missing the distance x but it is the apothem of the square and so it is half of the side, 3 cm. (3)2 + h2 = 52 h = 4 cm Now we can use the volume formula 1 Bh 3 1 = ( Base Area)( height ) 3 1 = (6)(6) (4) = 48 cm3 3 VolumePYRAMID = VolumePYRAMID VolumePYRAMID Another given instead of the height might be to have the length of the lateral edge. To do this type of question we can use the right triangle on the face of the pyramid to find the slant height, l and then use the slant height value to determine h. (5)2 + l2 = 132 l = 12 cm (5)2 + h2 = 122 h = 10.91 cm 1 Bh 3 1 = ( Base Area)( height ) 3 1 = (10)(10) (10.91) = 363.67 cm3 3 VolumePYRAMID = VolumePYRAMID VolumePYRAMID G.GMD.3 WORKSHEET #4 NAME: ____________________________ PERIOD ________ 1 1. Match the following terms to the diagram. Given the square pyramid. _________ 1. Slant Height _________ 2. Apex _________ 3. Height _________ 4. Lateral Edge _________ 5. Face _________ 6. Vertex 2. Jeff missed class and Dillon is explaining the notes. “The slant height and the height of the pyramid basically mean the same thing.” Is this summary of height correct? Explain. 3. Properly name the pyramid. a) b) c) d) Name: Name: Name: Name: _____________________ _____________________ _____________________ _____________________ 4. Two pyramids with the same base are side by side. One is a right pyramid and the other is an oblique pyramid. If the oblique pyramid has been tilted to an angle of 80°°, what is volume relationship between the two pyramids? G.GMD.3 WORKSHEET #4 2 5. Determine the volume of the pyramid. a) Square Pyramid b) Rectangular Pyramid c) Regular Hexagonal Pyramid Volume = ________________ Volume = _____________ (2 dec.) Volume = _________________ (E) d) Square Pyramid e) Equilateral Triangular Pyramid f) Square Pyramid Volume = ______________ (2 dec.) Volume = _________________ (E) Volume = _________________ (E) G.GMD.3 WORKSHEET #4 3 6. Determine the volume of the pyramid. a) Square Pyramid b) c) Volume = ________________ Volume = _____________ Volume = _______________ d) e) f) Volume = _________________ (E) Volume = _________________ Volume = _________________ (E) G.GMD.s woRKsHEEr #4 1. Match the following terms to the *o*r' diagram. W , period I ] - Given the square pyramid. ? 1. Slant Height 2. Apex €. 3. Height 4. Lateral Edge A 5. Face 6. Vertex 2. lett missed class and Dillon is explaining the notes. 'The slant height and the height of the pyramid basically mean the same thing." ls this summary of height correct? Explain. 3. Properly name the pyramid. a) b) I : ji /h rf : j\:-; .,r Name: {lwEr,wl Name: )?! Name: ?$vowiL 4. Two pyramids with the same base are side by side. One is a right pyramid and the other is an oblique pyramid. lf the oblique pyramid has been tilted to an angle of 80o, what is volume retationship between the two pyramids? 2 G.GMD.sWORKSHEET #4 5. Determine the volume of the pyramid' c) Regular Hexagonal PYramid b) Rectangular PYramid a)Square Pyramid ,"h 6cm 8Qn V= *3t^- , ta V= + xh- LD&)(tt) =+ = lLt volume = (t*p)L = + ?to\&r)(D = 6tlo rl7 lb? cu,? (2 dec.) Volume = e) Equilateral Triangular Pyramid d)Square Pyramid Ldercl tdge* t3 crn Volume= 6YuECW? (E) f)Square Pyramid /in t't'\ f ^T-\i _,fi 12 V=)o {ltl M L-. = 46afi\(n) = +pr,) dd6,) = b"\D Volume = (2 dec.) Volume = (E) Volume = (E) G.GMD.3 WORKSHEET #4 a 6. Determine the volume of the pyramid. a)Square Pyramid b) hTL-= $n h"+*' fl' fi: Li h=7 v. *bk w v{*r* + V73-'it ++fi|-,,.,-\ :frk -; 07)tti u ! (nt14trt = ! 0ol(o)('r) : 12fu rq : 12o + 3*V e Uof Votume = ll1o Cu9 d) Volume = Volume e) f) i\ ==-\ i\:-\ -a.i-a* \ \ -cl]f, arf .'a-\ [* : _; = (lAL ca> hogcm .a- 5cm V" *Tl*= +olqeru) =7o Volume = lr- (E) Volume = 7a Crt Volume = (E)
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