Answer:
9
It is 9 because 9 is the only number that multiplied by itself is 81.
D. 8 grams
The equation
Ending Amount = Beginning Amount / 2(time / half-life)
32/2^(6/3)
32/2^2
32/4
=8
Answer:
1.60 
Step-by-step explanation:
Assuming that this is a cylindrical pipe, the area can be determined by applying the formula for calculating the area of a circle.
i.e Area = 

So that,
for the inner part of the pipe,
r = 
= 
= 2.5 feet
Area of the inner part of the pipe = 

= 3.14 x 
= 19.625
Are of the inner part of the pipe is 19.63
.
Total diameter of the pipe = 5 + 0.2
= 5.2 feet
r = 
= 2.6 feet
Area of the pipe = 

= 3.14 x 
= 21.2264
Area of the pipe is 21.23
.
Thus the cross sectional area = Area of the pipe - Area of the inner part of the pipe
= 21.2264 - 19.625
= 1.6014
The cross sectional area of the cement pipe is 1.60
.