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## Sunday, August 22, 2010

### RGS Primary 2009 PSLE Math Prelim Paper 2 Q10

Some secondary one boys were asked to name their favourite sport. Their choices were represented on the pie chart below.

There was an equal number of boys who liked athletics and swimming. 80 boys chose football as their favourite sport.
a) What fraction of the boys liked swimming?
b) Find the total number of secondary one pupils who took part in the survey.

Solution

100% --> 360 degrees
1% --> 360 degrees divided by 100 = 3.6 degrees
(Rugby) 5% --> 5 x 3.6 degrees = 18 degrees

a)
Athletics --> (90 - 18) degrees = 72 degrees
Athletics --> same number as Swimming
Swimming --> 72 degrees

Fraction of boys who liked swimming
--> 72/360 = 1/5

b)
Football --> (100 - 25* - 20** - 15)% = 40%
40% --> 80
10 % --> 80 divided by 4 = 20
100% --> 10 x 20 = 200

*25% --> Athletics + Rugby (90 degress is 25% of 360 degrees)
**20% --> Swimming is 1/5 (20%)