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 Forum Index >  Test Paper Related >  Primary 6 Matters P6 Maths! 2012 Prelims St Hilda's Paper 2 Q 15 & 18
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 By: geniuskids (offline)  Monday, September 09 2013 @ 02:37 AM CDT (Read 1124 times)
geniuskids

Hi, pls help with solutions.

Answer key Q15) 16.04cm2 and Q18a) 111 (think is 111, not clearly stated) and 18b) 360

Thanks

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Registered: 11/12/11
Posts: 169

 By: jo sarah (offline)  Monday, September 09 2013 @ 07:39 AM CDT
jo sarah

Q18.

Let there be 40u passengers at Pasir Ris (PR).
At Tampines (T), 2/5 alighted, 80 boarded. So, at T: 24u + 80
At Simei (S), 223 alighted, 38 boarded, so at S: 24u + 80 - 223 + 38 = 24u - 105,
which is 3/8 of no. at T, and this is 3/8 x (24u + 80) = 9u + 30

So, 9u + 30 = 24u - 105
That is, 15u = 135
So that, 1u = 9

(a) There were 9 x 9 + 30 = 111 people when it left S.
[check: 24 x 9 - 105 = 111 ]

(b) When it left PR, there were 40 x 9 = 360 people.

Q15.
[it's difficult to redraw figure here, but hope you can follow...]

Call the unshaded region 'between' regions X and Y region A (unshaded part between arc and longest edge of isosceles triangle with equal sides of 10 cm)

Then, areas of.... X + A = area of quadrant - 0.5 x 10cm x 10 cm = quadrant - 50 ...........[1]
( I'm leaving out unit for easy typing)
And, areas of.......Y + A = 0.5 x 5 x 5 = 12.5..................................[2]
From [1] - [2]:
X - Y = quadrant - 50 - 12.5 = 0.25 x <pi> x 10 x 10 - 62.5 = 16.0398 = 16.04 cm2 (2 d.p.)

Hope this is clear and helpful, Cheerio!

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Registered: 03/20/12
Posts: 111

 By: geniuskids (offline)  Monday, September 09 2013 @ 11:25 PM CDT
geniuskids

Hi, I understand both Qs. now. Thank you

Active Member

Registered: 11/12/11
Posts: 169

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