Answer:
f(n)= 5 · 4

Step-by-step explanation:
You use the explicit formula for geometric sequence. The five is the firat term and is placed correctly. The 4 is the rate of change, because if you multiply 5 by 4 you get 20 and so on.
In order to get an 81 average,
the student has to get 81x5=405
71+96+90+73+?=405
330+?=405
405-330=75
he needs to get an 75
Answer:

Step-by-step explanation:
To find : Convert 110 km/myr (kilometers per million years) to cm/yr (centimeters per year) ?
Solution :
Using metric conversions,
1 kilometer = 1000 meter
1 meter = 100 centimeter
So, 1 kilometer = 100,000 centimeter
and 1 million year = 1,000,000 year


So, 

Therefore, 