1.1 Round the following numbers:

1.1.1 923.9804732 to 4 decimal places.
1.1.2 549.510 to the nearest whole number.
1.1.3 The price of an item is R18 390,8329. Round according to the context.

1.2 In a class, there are 30 girls and 18 boys. Give the ratio of boys to girls in the simplest form.

1.3 The SPCA says that they have 3 cats for every 5 dogs at the centre. If the centre buys 20 bags of dog food, calculate how many bags of cat food should the centre purchase.

1.4 Give the simplified rate for the following: Traveling 200km in 4 hours. (Simplify the hours.)

1.5 200g coffee cost R89,99 while 100g of coffee cost R54.99. Convert the 200g coffee to 100g to show that the 200g coffee is at a cheaper rate than the 100g coffee.

1.6 Calculate 30% of 850.

1.7 Peter got 28 out of 40 for a test. Calculate the percentage Peter got.

1.8 Increase R540 with 12%.

1.9 Decrease R650 with 5%.

1.1.1 Round 923.9804732 to 4 decimal places:
To round to 4 decimal places, we look at the fifth decimal place. The number is 923.9804__7__32. The fifth place is '7', which means we round up.
[tex]923.9804732 \approx 923.9805[/tex]

1.1.2 Round 549.510 to the nearest whole number:
Since the first decimal is '5', we round up from 549 to:
[tex]549.510 \approx 550[/tex]

1.1.3 The price of an item R18,390.8329 rounded according to the context:
In a monetary context, we typically round to 2 decimal places (cents). Looking at the third decimal place which is '2':
[tex]R18,390.8329 \approx R18,390.83[/tex]

1.2 Ratio of boys to girls:

There are 30 girls and 18 boys.
The ratio of boys to girls is 18:30.
Simplifying the ratio by dividing both numbers by 6 gives:
[tex]\text{Ratio} = \frac{18}{6} : \frac{30}{6} = 3:5[/tex]

1.3 Bags of cat food needed:

The ratio is 3 cats to 5 dogs. For 20 bags of dog food, which covers 5 dogs, use the ratio to determine cat food.
5 dogs correspond to 20 bags, hence 3 cats correspond to:
[tex]\frac{3}{5} \times 20 = 12 \text{ bags of cat food}[/tex]

1.4 Simplified rate for traveling 200km in 4 hours:

Calculate the rate as distance over time:
[tex]\text{Speed} = \frac{200\text{ km}}{4\text{ hours}} = 50\text{ km/h}[/tex]

1.5 Convert the cost of 200g coffee to 100g:

If 200g costs R89.99, we find the cost per 100g by dividing by 2:
[tex]\text{Cost per 100g for 200g pack} = \frac{89.99}{2} = R45.00[/tex]
Comparing R45.00 (100g of 200g pack) and R54.99 (original 100g cost), the 200g pack is cheaper per 100g.

1.6 Calculate 30% of 850:

Convert the percentage to a decimal and multiply:
[tex]0.30 \times 850 = 255[/tex]

1.7 Peter's test percentage:

He scored 28 out of 40, calculate the percentage:
[tex]\left(\frac{28}{40}\right) \times 100 = 70\%[/tex]

1.8 Increase R540 by 12%:

Increase by calculating 12% of R540 and adding it:
[tex]R540 \times 0.12 = R64.80[/tex]
Therefore, new price is:
[tex]R540 + R64.80 = R604.80[/tex]

1.9 Decrease R650 by 5%:

Decrease by calculating 5% of R650:
[tex]R650 \times 0.05 = R32.50[/tex]
Therefore, new price is:
[tex]R650 - R32.50 = R617.50[/tex]