J's answer to Rozi's Primary 6 Maths Measurement Singapore question.

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J
J's answer
1024 answers (A Helpful Person)
Notice the shaded areas are equal to the unshaded areas. You can fit them into one side of the square.
The shaded area is just half a square minus a semicircle.
(6cm x 12cm) - (π x 6cm x 6cm x ½)
= 72cm² - 56.5486678cm²
= 15.4513322cm²
≈ 15.45cm² (2 decimal places)