Primary 6 · Circle · Question type 6.6
If one shape fits exactly inside another, their touching lengths are equal.
Try the question yourself, or watch the lesson first.
Primary 6, on the MOE Primary Mathematics syllabus.
The lesson · 2 minutes 16 seconds
Watch: the area of a circle that fits exactly inside a square
Another worked example
A quadrant is painted on a wall. The quadrant has an area of 78.5 cm². Find the diameter of the full circle that the quadrant was cut from. (Take π = 3.14.)
The working · Five lines
Written out in full, the way it should appear on paper.
The answer is 20 cm.
Practise · Modelled on top school exam questions
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Try it yourself
Use the row of touching circles to recover one cap's diameter before finding its area.
Five identical circular bottle caps lie touching in a straight row, and the row spans 35 cm from the left rim of the first cap to the right rim of the last. Find the area of one cap. (Take π = 3.14.)
Ans: 38.465 cm²
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