Answer:
7. 20,000,000 mL. 
8. 8,000 m. 
9. 120,000 secs. 
10. 4
Explanation:
7. Determination of the volume in millilitres (mL)
Volume in litre (L) = 20,000 L 
Volume in millilitres (mL) =..? 
The volume in mL can be obtained as follow:
1 L = 1,000 mL
Therefore, 
20,000 L = 20,000 x 1,000 = 20,000,000 mL. 
Therefore, 20,000 L is equivalent to 20,000,000 mL.
8. Determination of the distance in metre (m) 
Distance in mile = 5 mile 
Distance in metre =? 
First, we shall convert from mile to kilometre. 
This can be done as follow:
1 mile = 1.6 km
Therefore, 
5 mile = 5 x 1.6 = 8 km
Finally, we shall convert 8 km to metre (m). 
This is illustrated below:
1 km = 1,000 m
Therefore, 
8 km = 8 x 1,000 = 8,000 m
Therefore, 5 miles is equivalent to 8,000 m.
9. Determination of the time in seconds. 
Time = 400 minutes for 5 days. 
First, we shall convert 400 mins to hour. 
This is illustrated below:
60 minutes = 1 hour 
Therefore, 
400 mins = 400/60 = 20/3 hours
The time (hours) is 20/3 hours in 1 day. 
Therefore, the time (hours) in 5 days will be = 20/3 x 5 = 100/3 hours. 
Next, we shall convert 100/3 hours to minutes. 
This is illustrated below:
1 hour = 60 minutes 
Therefore, 
100/3 hours = 100/3 x 60 = 2000 mins 
Finally, we shall convert 2000 mins to seconds.
This is illustrated below:
1 mins = 60 secs 
2000 mins = 2000 x 60 = 120,000 secs. 
Therefore, the time is 120,000 secs.
10. Determination of the number of significant figures. 
To obtain the significant figures of a number, we simply count all the numbers available. 
Therefore, the number of significant figures for 9876 is 4.