Answer :
Let's solve each part of the question step by step.
Cost of 10 pens:
The girl buys 7 pens for #630. So, the cost of one pen is [tex]\frac{630}{7} = 90[/tex] #.
To find the cost of 10 pens, multiply the cost of one pen by 10:
[tex]90 \times 10 = 900 \text{ #}[/tex]
So, 10 pens would cost 900 #.
Trips for a 5-tonne lorry:
A 3-tonne lorry takes 10 trips. This means a total weight of 30 tonnes is moved. Let's find out how many trips a 5-tonne lorry would take.
Divide the total weight by the new lorry's capacity:
[tex]\frac{30}{5} = 6 \text{ trips}[/tex]
Time for a 6-year-old to run 100m:
Running time depends on factors like age, fitness, etc., but since there isn’t enough information to calculate this, we cannot provide an exact time for the 6-year-old.
Feeding 80 chickens:
A bag feeds 100 chickens for 12 days. Therefore, the total 'chicken-days' covered is [tex]100 \times 12[/tex].
For 80 chickens, divide the total 'chicken-days' by 80:
[tex]\frac{1200}{80} = 15 \text{ days}[/tex]
Filling a drum with 7-litre buckets:
It takes 21 buckets of 9-litres. So, the drum's capacity is [tex]21 \times 9 = 189 \text{ l}[/tex].
To see how many 7-litre buckets it takes, divide the drum capacity by 7:
[tex]\frac{189}{7} = 27 \text{ buckets}[/tex]
Travel time at 90 km/h:
At 60 km/h, the journey takes 5 hours. Thus, the distance is [tex]60 \times 5 = 300 \text{ km}[/tex].
At 90 km/h, divide the distance by the new speed:
[tex]\frac{300}{90} = \frac{10}{3} = 3.33 \text{ hours}[/tex]
Thickness of 380 pages:
If 480 pages are 2.4 cm thick, the thickness per page is [tex]\frac{2.4}{480} \text{ cm}[/tex].
Multiply this by 380:
[tex]\frac{2.4}{480} \times 380 = 1.9 \text{ cm}[/tex]
Feeding 10 students:
One bag feeds 15 students for 7 days, equivalent to 105 student-days.
For 10 students, divide by 10:
[tex]\frac{105}{10} = 10.5 \text{ days}[/tex]
Trips for 3 buses:
Five buses taking 3 trips handle 15 bus-trips.
For 3 buses, divide the total by 3:
[tex]\frac{15}{3} = 5 \text{ trips}[/tex]