AC Lim's answer to Chris's Primary 6 Maths Ratio Singapore question.
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Hope this helps
Date Posted:
4 years ago
Thank you
May I know why do we need to multiply by 4?
Square given is 3u ... 1/4 of 3u = 1/4 x 3u = 3u/4 give you a fraction. Since is ratio(fraction) we x4 to get a easy number for calculation.
You can do without x4 too
For square
Shaded area, 1/4 x 3u = 3u/4
Unshaded area, 3u - 3u/4 = 9u/4
For triangle
Total area =2u
Unshaded area = 2u - 3u/4= 5u/4
Shaded area is same = 3u/4
Total figure area
= square unshaded + shaded + triangle unshaded
= 9u/4+3u/4+5u/4= 17u/4
Fraction = (3u/4) / (17u/4) = 3/17.
You can do without x4 too
For square
Shaded area, 1/4 x 3u = 3u/4
Unshaded area, 3u - 3u/4 = 9u/4
For triangle
Total area =2u
Unshaded area = 2u - 3u/4= 5u/4
Shaded area is same = 3u/4
Total figure area
= square unshaded + shaded + triangle unshaded
= 9u/4+3u/4+5u/4= 17u/4
Fraction = (3u/4) / (17u/4) = 3/17.
Thank you so much. Totally understand, thought might be a Long way.
Yes. We alway look for common multiple. For this question, we look for common multiple of 3 and 4.
Noted, thank you.
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