Katelyn
had some green, red and blue ribbons. She had 25% more green ribbons
than red ribbons and 20% less blue ribbons than red ones.

a) What is the ratio of red ribbons to green ribbons to blue ribbons?

b)
Katelyn exchanges all her blue ribbons for some red and green ribbons.
She now has an equal number of red and green ribbons. How many more
green than red ribbons did she have at first if she has 244 red ribbons
now?

Solution

(a)

Red ----- 100%

Green ----- 25% more than 100% = 125%

Blue ----- 20% less than 100% = 80%

Red : Green : Blue

100 : 125 : 80

20 : 25 : 16

Answer: 20 : 25 : 16

(b)

Before Katelyn exchanges,

Red : Green : Blue

20 : 25 : 16

Blue
exchanged for green and red will mean that 16 units of blue will be
given up. Since Katelyn finally has an equal of number red and green, 5
units of the 16 units of blue will be exchanged for red first, with the
remaining 11 units divided equally between red and green.

Red will receive ----- 5 units + (11 units divided by 2) = 10.5 units

Green will receive ----- 11 units divided by 2 = 5.5 units

Red ribbons now ----- 20 units + 10.5 units = 30.5 units

30.5 units ----- 244

1 unit ---- 244 divided by 30.5 = 8

In the beginning,

Green - Red

25 units - 20 units = 5 units

5 units ----- 5 x 8 = 40

Answer: 40 red ribbons

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This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

## Wednesday, September 12, 2012

### Red Swastika Sch 2011 PSLE Math Prelim Paper 2 Q10

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