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 Forum Index >  Test Paper Related >  Primary 5 Matters Nanyang SA2 2012 Q16 n Q17 B
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 By: zinmkw (offline)  Wednesday, October 02 2013 @ 05:00 AM CDT (Read 1950 times)
zinmkw

Q 16)
?The mass of rice? bag B was 0.25 the mass of rice A at first. After 105 kg of the rice in Bag A and 20 Kg 300 g of rice in Bag B was used, the mass of rice in Bag A was 1/2 the mass of rice in bag B.

a) How much rice was left in Bag B at he end? ]Ans 6.8kg

b) What was the total mass of rice in Bag A and B at first? Ans 135.5 Kg

Q 17)
A shop sold blocks of metal in the form of a cuboid. Each block of metal measured 19 cm by 3cm by 2 cm.
Mr Gopal bought some blocks of metal from the shop. He melted the blocks of metal into liquid metal and recast it into cubes, each with an edge of 2cm.
The maximum number of cubes that he managed to recast is 42.

b) If Mr Gopal used all of the 42 cubes to build a cuboid in which the perimeter of its base was 20cm, what was the height of cuboid? Ans 14

According to answer sheet already got ans but still cannot understand the step, pls help me to explain

Newbie

Registered: 10/11/10
Posts: 7

 By: zinmkw (offline)  Wednesday, October 02 2013 @ 06:51 AM CDT
zinmkw

FOR Q17B I FOUND OUT THE SOLUTION N EXPLANATION AT KIASUPARETS.COM
THKS

Newbie

Registered: 10/11/10
Posts: 7

 By: echeewh (offline)  Wednesday, October 02 2013 @ 07:25 PM CDT
echeewh

Hi <zinmkw>

Following is my worked solution for Q16:

Q16.

<before>
A : B
4 : 1

<process>
A: -105 kg
B: - 20.3 kg

<after>
A : B
1 : 2

This is a <Changed Qtys> concept type of question as the qtys in both A, B are decreased. From this model (given the ratios), we can use the <Cross Multiply > method to solve it.

(4u - 105) / 1 = (1u - 20.3) / 2
2 × (4u - 105) = (1u - 20.3)
8u - 210 = 1u - 20.3
8u - 1u = 210 - 20.3
7u --> 189.7
1u --> 27.1

(a)
B (at the end)
= 1u - 20.3 --> 27.1 - 20.3 = 6.8 kg

(b)
A + B (at first)
= 5u --> 5 × 27.1 = 135.5 kg

=========

Trust this helps.

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

Cheers,
Edward

Active Member

Registered: 04/21/11
Posts: 623

 By: zinmkw (offline)  Thursday, October 03 2013 @ 06:49 AM CDT
zinmkw

Thank u so much for clear explanation, now understand concept.

Newbie

Registered: 10/11/10
Posts: 7

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