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Classroom activity Grade 10 Art & Music

Nettle Brook Watershed Mural: A Grade 10 Grid-Enlargement Relay

A grade 10 team activity where students enlarge a watershed master drawing onto a wall grid with the grid method, calculating scale factor and finished size.

Objectives

  1. Students will enlarge a master drawing onto a wall grid using the grid method.
  2. Students will calculate the scale factor and finished size of a gridded mural.
  3. Students will map a point from the master grid to the wall grid using coordinates.

Vocabulary

Key words: grid method, scale factor, coordinate, proportion

Teacher overview

This is a team relay for groups of five that turns the grid method, a centuries-old enlargement technique, into a shared mural build. Each team enlarges a small master drawing of the fictional Nettle Brook watershed onto a wall grid, where every small square maps to a larger square in the same position. The activity teaches the concept directly: because the same scale factor governs every square, the enlargement stays in proportion no matter how many hands work on it, which is exactly why the grid method keeps a large mural true to its small original.

Activity Directions

  1. Introduce the concept (8 min): Show the master drawing of the Nettle Brook watershed with its 2-inch grid, and the wall marked in a matching 1-foot grid. Explain that each small square becomes one large square in the same row and column, and that every square uses the same scale factor, so the picture keeps its proportions.
  2. Set up (7 min): Post the master drawing where all teams can see it. Give each team its own 4-by-5-foot wall grid of 20 squares. Form teams of five and number the painters 1 through 5.
  3. Calculate first (10 min): Before anyone paints, each team completes the handout, finding the scale factor, the finished mural size, each painter's share of squares, and the coordinate mapping in item 6. Check a team's scale factor before releasing it to paint.
  4. Transfer relay (22 min): In turns, each numbered painter transfers the contents of their assigned master squares into the matching wall squares, then hands the marker to the next painter. Painters copy only what falls inside their squares, trusting the grid to keep the whole in proportion.
  5. End condition: The activity ends when every wall square in a team's grid has been transferred, or when the 22-minute build timer runs out, whichever comes first.
  6. Debrief (8 min): Gather teams at the wall and run the debrief questions below.
Nettle Brook Watershed Mural: A Grade 10 Grid-Enlargement Relay — Grade 10 Art & Music
Name: ____________________________ Date: ______________

Student Handout

Your team is painting a mural of the fictional Nettle Brook watershed. The master drawing is 8 inches wide and 10 inches tall, divided into a grid of 2-inch squares. On the wall, each 2-inch master square becomes a 12-inch (1-foot) square. Answer each item.

  1. How many 2-inch squares run across the width and down the height of the master grid, and how many squares are there in total?
  2. A 2-inch master square becomes a 12-inch wall square. What is the scale factor from the master grid to the wall grid?
  3. How wide and how tall is the finished mural, in feet?
  4. What is the area of the finished mural, in square feet?
  5. The 20 wall squares are shared equally among a team of 5 painters. How many squares does each painter transfer?
  6. A shape's corner sits at grid point (3, 4), counting squares from the bottom-left corner of the master grid. On the wall grid, where is that same corner, measured in feet from the bottom-left corner?

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 20 squares. The width holds 8 divided by 2, or 4 squares; the height holds 10 divided by 2, or 5 squares; and 4 times 5 equals 20 squares.
  2. Answer: 6. The square grows from a 2-inch side to a 12-inch side, and 12 divided by 2 equals a scale factor of 6.
  3. Answer: 4 feet by 5 feet. The width is 8 inches times 6, or 48 inches, which is 4 feet; the height is 10 inches times 6, or 60 inches, which is 5 feet.
  4. Answer: 20 square feet. The finished mural is 4 feet by 5 feet, and 4 times 5 equals 20 square feet.
  5. Answer: 4 squares. The 20 wall squares divided among 5 painters give 20 divided by 5, or 4 squares each.
  6. Answer: (3 feet, 4 feet). Each wall square is 1 foot, so the master point (3, 4) maps to 3 feet across and 4 feet up from the bottom-left corner.

Debrief question: Why does the mural stay in proportion even though five painters work on different squares? Answer: Every square uses the same scale factor of 6, so each part enlarges by the same amount and the pieces fit together correctly.

Debrief question: How would the finished mural change if each square became 18 inches instead of 12? Answer: The scale factor would be 9 instead of 6, so the mural would be larger, 6 feet by 7.5 feet, while keeping the same proportions.

Differentiation

Support

Give students the scale factor of 6 already found before item 3, and provide the master grid with rows and columns already numbered so the coordinate mapping in item 6 is easier to trace. Pair a stronger drafter with each relay team.

Extension

Ask students to recalculate the finished mural size and area if the master square is unchanged but each wall square is set to 18 inches, and to explain why the area grows by the square of the change in scale factor rather than in proportion to it.

ELL supports

Provide a bilingual card for "grid," "scale factor," "coordinate," and "proportion," each with a small image. Demonstrate one square's transfer at the wall before the relay begins, and allow team members to point to their assigned squares rather than describe them in words.