Univia M.'s answer to Oliver's Primary 5 Maths Rate & Ratio Singapore question.
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I hope this is correct cuz i’m P6:)
Date Posted:
4 years ago
Final answer is incorrect. Your approach to solving is correct but you've mistaken the diameter of the big unshaded circle to be 12cm instead of 15cm.
Also, there is a calculation error in your second last step. It should be 176.625cm² instead of 149.625cm².
Notice that the 15cm line cuts across the centre of the large unshaded circle. So the diameter is 15cm and therefore radius is 7.5cm
Tip :
Two semicircles of the same size can be combined into a single circle. So in your working, you can just write
½ x 3.14 x 6 x 6 x 2
Or
3.14 x 6 x 6
in a single step instead of dividing by ½ to find one semicircle and then multiplying by 2 again
Also, there is a calculation error in your second last step. It should be 176.625cm² instead of 149.625cm².
Notice that the 15cm line cuts across the centre of the large unshaded circle. So the diameter is 15cm and therefore radius is 7.5cm
Tip :
Two semicircles of the same size can be combined into a single circle. So in your working, you can just write
½ x 3.14 x 6 x 6 x 2
Or
3.14 x 6 x 6
in a single step instead of dividing by ½ to find one semicircle and then multiplying by 2 again
thats right, thanks
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