Advanced Mathematics Primary 4 Symmetry

An L-shaped figure is drawn on a square dot grid. Its vertices are at A(1,1), B(1,5), C(2,5), D(2,2), E(4,2) and F(4,1). The vertical line x = 6 is the mirror line. When the L-shaped figure is reflected across this mirror line, what are the coordinates of the image of vertex B?

A (11, 5)
B (1, 5)
C (5, 5)
D (7, 5)
Show Worked Solution

Worked Solution

Step 1: Identify the mirror line. The mirror line is the vertical line x = 6. Step 2: Find the reflected x-coordinate of vertex B(1, 5). For a reflection across a vertical line x = k, the formula is: x' = 2k − x x' = 2 × 6 − 1 = 12 − 1 = 11 Step 3: The y-coordinate does not change for a vertical mirror line. y' = 5 Step 4: Write the coordinates of the image of B. B' = (11, 5) Answer: (11, 5)

Correct answer: (11, 5)

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