Justifying the steps
Types of exercises: justifying the steps - area and perimeter formulas.
Exercises are drawn at random from a large bank - every click gives a different set.
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Which reason fits this step?
A rectangle has sides of 5 cm and 11 cm. What is its area? A pupil wrote: A = 5 · 11 = 55 cm²
Which reason fits this step?
A rectangle has sides of 15 cm and 6 cm. What is its perimeter? A pupil wrote: P = 2 · 15 + 2 · 6 = 42 cm
Which reason fits this step?
A trapezium has parallel sides of 14 cm and 6 cm, and its height is 4 cm. What is its area? A pupil wrote: A = (14 + 6) · 4 : 2 = 40 cm²
Which reason fits this step?
A triangle has a base of 11 cm, and the height drawn to that base is 8 cm. What is its area? A pupil wrote: A = 11 · 8 : 2 = 44 cm²
Which reason fits this step?
A square has sides of 13 cm. What is its area? A pupil wrote: A = 13 · 13 = 169 cm²
Which reason fits this step?
A parallelogram that is not a rectangle has a base of 8 cm, and the height drawn to that base is 12 cm. What is its area? A pupil wrote: A = 8 · 12 = 96 cm²
Which reason fits this step?
A parallelogram that is not a rectangle has a base of 13 cm, and the height drawn to that base is 6 cm. What is its area? A pupil wrote: A = 13 · 6 = 78 cm²
Which reason fits this step?
A triangle has a base of 11 cm, and the height drawn to that base is 12 cm. What is its area? A pupil wrote: A = 11 · 12 : 2 = 66 cm²
Which reason fits this step?
A parallelogram that is not a rectangle has a base of 11 cm, and the height drawn to that base is 14 cm. What is its area? A pupil wrote: A = 11 · 14 = 154 cm²
Which reason fits this step?
A rectangle has sides of 9 cm and 5 cm. What is its perimeter? A pupil wrote: P = 2 · 9 + 2 · 5 = 28 cm
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