8-9 6 th grade math Scale Drawings

Objective To interpret scale drawings Why? To know how to interpret blueprints or scale drawings.

California State Standards NS 1.3 : Use proportions to solve problems (e.g. … find the length of a side of a polygon similar to a known polygon). Use cross-multiplication as a method for solving such problems… MR 2.4: Use a variety of methods, such as words, numbers, symbols, … diagrams, … to explain mathematical reasoning. MR 3.2: Note the method of deriving the solution and demonstrate a conceptual understanding of the derivation by solving similar problems.

Vocabulary Scale drawing – A drawing made so that actual measurements can be determined from the drawing by using the scale. Blue prints, drawings shrunk from the ‘real’ size Scale – The ratio of the measurements in a drawing to the measurements of the actual objects On maps: 25 miles for each 1 inch

How to Solve Scale Drawings 1)Write a proportion using the scale as one of the ratios. Let n or x = the actual length. Be consistent with the set up of your proportions. 2) Solve the proportions. Use cross products 3) Check answer for reasonableness. Scale: 1 cm = 10 m drawing = drawing actual 1 cm = 9.5 cm 10 m x m x = 95 m Scale: 1 cm = 10 m drawing = actual drawing actual 1 cm = m x x = 95 m Same answer, but different ‘set-up”

Try It! Scale: 1 cm = 10 m 1)Length of penalty box, 1.5 cm, actual = ? 2)Width of field, 5.6 cm, actual = ? 3)Width of stands, 62.5 m, scale = ? 1) 1 = x x = 15 m 2) 1 = x x = 56 m 3) 1 = x x = 62.5 x = 6.25 cm

Objective Review To interpret scale drawings Why? You now know how to interpret blueprints or scale drawings. Proportions can be used to find actual measurements of objects shown on scale drawings and to find scaled-down measurements for scale drawings. Be sure to write up your ratios or proportions equally or the same.

Independent Practice Complete problems Copy original problem first. Show all work! If time, complete Mixed Review: If still more time, work on Accelerated Math.