Class 8 Plotting Points — practice questions with answers

Coordinate Geometry · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.

1. In the ordered pair (4, 7), what is the x-coordinate?

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Answer: A) 4

In an ordered pair (x, y), the first number is the x-coordinate. So in (4, 7) the x-coordinate is 4.

2. Which of these ordered pairs represents the SAME point as (2, 5)?

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Answer: A) None of these

An ordered pair is fixed by order. (5,2), (2,-5) and (-2,5) are all different points from (2,5), so none of them match.

3. If a point is reflected from Quadrant I to Quadrant IV across the x-axis, what changes?

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Answer: A) The sign of the y-coordinate

Reflecting across the x-axis keeps x the same and changes the sign of y. So (a, b) becomes (a, -b).

4. A rectangle is plotted with corners at (1, 1), (9, 1), (9, 5) and (1, 5).
What is its perimeter, in units?

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Answer: B) 24

Length = 9 - 1 = 8 units, breadth = 5 - 1 = 4 units. Perimeter = 2(8 + 4) = 2 x 12 = 24 units.

5. A trapezium has vertices P(0, 0), Q(8, 0), R(6, 4) and S(2, 4), each unit being 1 cm. The two parallel sides are PQ and SR.
Using area =

\frac{1}{2}

x (sum of parallel sides) x height, find the area in square cm.

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Answer: C) 24

PQ = 8 - 0 = 8 cm; SR = 6 - 2 = 4 cm. Height (gap between the parallel sides) = 4 - 0 = 4 cm. Area =

\frac{1}{2}

x (8 + 4) x 4 =

\frac{1}{2}

x 12 x 4 = 24 sq cm.

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