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primary 6 | Maths | Percentage
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Dylan
Dylan

primary 6 chevron_right Maths chevron_right Percentage chevron_right Singapore

Please help!ASAP!

Date Posted: 4 years ago
Views: 367
Eric Nicholas K
Eric Nicholas K
4 years ago
There is no change in the number of red pens, but somehow because 15 green pens are removed, the percentage of red pens increases from 60% to 80%.

Old ratio of green : red is 40 : 60, or 2 : 3.
New ratio of green : red is 20 : 80, or 1 : 4.

But then, because the actual number of red pens is unchanged, we must make the “3” and “4” in our ratios the same.

We rewrite 2 : 3 as 8 : 12 and 1 : 4 as 3 : 12.

This means that there are 12 units of red pens and there is a decrease in the number of green pens from 8 units to 3 units.

So, 5 units = 15 pens
1 unit = 3 pens

In total, there are 20 units of pens at first, or 20 x 3 = 60 pens at first (consisting of 24 green pens and 36 red pens at first).

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goodsamathritan
Goodsamathritan's answer
745 answers (Tutor Details)
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As Mr Eric said, this uses ‘one side unchanged’.