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 Forum Index >  Test Paper Related >  Primary 6 Matters
 2013 Prelims ! P6 Maths! RGPS Paper 2 Q13(b) & 16
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By: geniuskids (offline)  Saturday, September 21 2013 @ 09:28 AM CDT (Read 774 times)  
geniuskids

Hi there, I need help on these 2 questions. Pls refer to attached!

Answer key
Q13 a) 16cm (Managed to get the answer)
13 b) 14.5cm (Need help on this)

Q16 a) 5:7 (don't understand this part, hence could not solve part b)
16 b) 63

Kindly explain! Thank you

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By: echeewh (offline)  Saturday, September 21 2013 @ 06:20 PM CDT  
echeewh

Hey <geniuskids>,

//updated 22/9, 09 00

Following are my worked solutions:

Q13.

(a)
Vol of Water(W) = 240 × 5 = 1200 cm3

Let the height of water be h cm
Vol of cuboid(C) = 5 × 5 × h = 25h

Vol water in tank
= 10 × 10 × h
= 100h -- (1)

This is the same as ..
Vol of cuboid (in water) + Vol of water
= 25h + 1200 -- (2)

(1)=(2)
100h = 25h + 1200
100h - 25h = 1200
75h = 1200
h = 1200 ÷ 75
= 16 cm

(b)
Vol occupied by 1 cuboid + water
= (5 × 5 × 10) + 1200
= 250 + 1200
= 1450

Height of water in tank (after top cuboid removed)
= 1450 ÷ 100
= 14.5 cm

==========

Q16.

*** - for alignment purpose

(a)

<before>
A : C
5 : 7

<64A , 84C entered the event hall>

A : C
60 : 84
5 : 7

Since the same ratio of A : C entered the event hall, the <after> ratio remains unchanged.

<After>

A : C * Diff
5 : 7 ** 2 -- (1)

A : C (in event hall)
5 : 7

(b)
<56A, 56C left event hall>

<after1>

A : C
7 : 13 * 6 -- (2)

Apply <Unchanged Difference> concept here , i.e difference between A , C <before> and <after>.

(1)x3:

<before>

A : C
15 : 21* 6 -- (3)

Comparing (3),(2) shows the following:
A: 15u - 7u = 8u
C: 21u - 13u = 8u

8u --> 56
1u --> 7

Number of Children(C) (at first):
= 21u --> 21 × 7 = 147

Before 84C entered the event hall,
147 - 84 = 63

========

Trust this helps.

Do let me know again If there's further clarification.

Cheers,
Edward

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