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Friday, July 21 2017 @ 03:36 PM CDT
 Forum Index >  Test Paper Related >  Primary 6 Matters
 P6 decimals & ratio
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By: JessicaTan (offline)  Tuesday, February 26 2013 @ 05:05 AM CST (Read 600 times)  
JessicaTan

Please help with working solution.

10) A faulty weighing scale showed a reading of 0.2kg when nothing was placed on it. A box which contained 21 identical books was placed on the weighing scale. After 5/7 of the books were removed from the box, the weighing scale showed a reading of 16.68kg. Given that the mass of each book was half the mass of the box, find the mass of the box.



11) A fruit seller had 630 apples & oranges. The ratio of the number of apples to the number of oranges was 4 : 5. He sold some oranges and gave his friend 50 apples. The ratio of the number of apples to the number of oranges left became 5 : 2. How many fruits had he left?


thanks

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By: echeewh (offline)  Tuesday, February 26 2013 @ 09:53 PM CST  
echeewh

Hey Jessica,

Following pls find my worked solutions:

Q10

(5/7) books removed; (2/7) books left.
(2/7) × 21 = 6
(6 books + B ) weighed (16.68 - 0.2)kg = 16.48 kg

Given that the mass of each book was half the mass of the box (B ),

1 book = (1/2) B
B = 2 books

So, 8 books = 16.48 kg
1 book = 16.48 ÷ 8 = 2.06
B = 2 books = 2 × 2.06 = 4.12 kg

=================

Q11

<before>
A : O
4 : 5

A = (4/9) × 630 = 280
O = 630 - 280 = 350

<process>
50 A given away.

A (left) = 280 - 50 = 230

<after>
A : O
5 : 2

Since there were 230 A left, we have ...

5u --> 230
1u --> 46

O (left) = 2u --> 2 × 46 = 92

Total fruits (left) = 230 + 92 = 322

==================

Trust the above helps.

Do let me know again if these are different from your Answerkey or if there's further clarification.

Cheers,
Edward.

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