A scale such as one inch to four feet applies to lengths, and that is where this topic hides its best-known mistake: areas scale by the square of the factor.
If a drawing's lengths are one-tenth of the real ones, its areas are one-hundredth. Transformations move figures on the coordinate plane. Rotating a figure half a turn about the origin changes the signs of both coordinates, a reflection across the y-axis changes only the sign of x, and a translation shifts every point the same distance.
Scale drawings and transformations questions may combine two moves in a row, so each step should be applied in order.
Sample questions
Pick an answer to see whether it is right — nothing is saved, and nothing needs an account.
Question 1Harder
A garden is shown on a drawing with a scale of 3 cm to 8 m. The real garden covers 128 square meters. What area does it occupy on the drawing?
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Answer: B — 18 cm2
Areas scale by the square of the length ratio: 9 cm2 stands for 64 m2, so 128 m2 becomes 2×9=18 cm2.
Question 2Mid
A figure is rotated 180∘ about the origin and then reflected across the y-axis. Where does the point (a,b) end up?
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Answer: A — (a,−b)
The rotation gives (−a,−b), and reflecting across the y-axis negates the first coordinate again, giving (a,−b).
Question 3Easier
Point R(−1,2) is rotated 180 degrees about the origin. Where is the image of R?
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Answer: A — (1,−2)
Apply the coordinate rule for the stated move to obtain (1,−2).
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