J's answer to Jovel's Primary 6 Maths Percentage Singapore question.
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See the two triangles?
Subtract the area of one triangle from area of one quarter circle.
Then you'll notice there are a total of 4 of the same shaded portions. So just need to multiply by 4 to get the total area of the shaded parts
Subtract the area of one triangle from area of one quarter circle.
Then you'll notice there are a total of 4 of the same shaded portions. So just need to multiply by 4 to get the total area of the shaded parts
Date Posted:
4 years ago
Since radius = 7cm,
Area of one quarter circle
= ¼ x 22/7 x 7cm x 7cm
= 38½cm²
Area of one triangle
= ½ x 7cm x 7cm
= 24½cm²
One smaller shaded portion
= 38½cm² - 24½cm²
= 14cm²
There are 4 of the same kind of smaller shaded portions in total.
So total area of shaded parts
= 14cm² x 4 = 56cm²
Alternatively,
The two triangles make up 1 bigger triangle.
Area of semicircle = ½ x 22/7 x 7cm x 7cm
= 77cm²
Area of bigger triangle
= ½ x 14cm x 7cm
= 49cm²
77cm² - 49cm² = 28cm²
After subtracting you'll get 2 of the shaded portions. There are 4 of them so you'll multiply by 2 .
28cm² x 2 = 56cm²
Area of one quarter circle
= ¼ x 22/7 x 7cm x 7cm
= 38½cm²
Area of one triangle
= ½ x 7cm x 7cm
= 24½cm²
One smaller shaded portion
= 38½cm² - 24½cm²
= 14cm²
There are 4 of the same kind of smaller shaded portions in total.
So total area of shaded parts
= 14cm² x 4 = 56cm²
Alternatively,
The two triangles make up 1 bigger triangle.
Area of semicircle = ½ x 22/7 x 7cm x 7cm
= 77cm²
Area of bigger triangle
= ½ x 14cm x 7cm
= 49cm²
77cm² - 49cm² = 28cm²
After subtracting you'll get 2 of the shaded portions. There are 4 of them so you'll multiply by 2 .
28cm² x 2 = 56cm²
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