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**

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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**

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Trust the above helps.

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

Cheers,

Edward.