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Geometry and Measurement 6-8 / Week 05 / Build Day
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Week 05 · Scale Drawings

Build Day

Build Day: The room plan
// The whole garage on one page
⏱ about 20 min

Build Day: The Room Plan

Saturday at the Blueprint Table, Raven hands the tape measure to Rocket's cousin. "Build Day. Pick a room and draw it to scale."

"Measure the longest wall first," Rocket says, "so you can pick the scale."

"What do you notice about the paper?" Raven asks. "It is 20 centimeters wide."

"A 500 centimeter wall needs 1 cm to 25 cm," the cousin says. "Then it is 20. Just fits."

Nova hovers above the grid paper. "Leave room for labels," she says. "A snug fit has no edges."

"1 to 50 then," the cousin says. "Ten centimeters, with space."

Nova hums. "Now every wall, the door and the window."

  1. A scale drawing keeps every shape and shrinks every length by one factor.
  2. Real to drawing: divide by the scale number. Drawing to real: multiply by it.
  3. Find a scale from any matching pair: real length divided by drawn length.
  4. Areas scale twice: lengths × 50 means area × 2,500.
  5. To redraw at a new scale, go back to the real lengths first.
◇ THE ROOM PLAN WITH A GROWN-UP
Pick a room. Measure each wall, the door and one window with the tape measure. Write every length.
Pick a scale that fits your paper with room for labels. Divide every length by the scale number.
Draw the room on grid paper, with the door and window in the right places. Label each real length.
Finish by finding the real floor area, and the drawn area, and the number you multiply between them.
For a grown-up
This week your student learned to draw to scale, to pick a scale and to compare real and drawn areas.
Ask them why the floor area is 2,500 times the drawn area at 1 cm to 50 cm. Listen for "50 times 50".
Hold the tape measure end so it never snaps back. Nobody stands on chairs to measure.
Safety first
The tape measure slides back slowly, with a hand on the end.
Measure at floor and table height only. Shoes on while measuring.
BUILD DAY CHECK
  • Read the question.
  • Tap your answer.
A wall is 500 cm. At 1 cm to 50 cm, how long is it on the plan, in cm?
A doorway is 2 cm on a 1 cm to 25 cm plan. How wide is the real doorway, in cm?
A 4 cm line on the drawing stands for 200 cm on the floor. The scale is 1 cm to how many cm?
A shape has area 20 square centimeters. Every length is multiplied by 5. What is the new area in square centimeters?
A room is 350 cm long. At 1 cm to 50 cm, how long is it on the plan, in cm? Type the number.
WHY THIS EXERCISE350 ÷ 50 = 7 centimeters on the page.
Draw your room plan with its scale written in a corner, like "1 cm to 50 cm".

Great drawing, crew. Next week the straws come out and the roof triangles begin.

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