A fuel is purified by passing it through a clay pipe. Each foot of the clay pipe removes a fixed percentage of impurities in the fuel. Let f(x) represent the amount of pollutants, in tons, left in the fuel after it had passed through x feet of the clay pipe:

Question

anonymous · Answer

$$f(x) = 10(0.8)^{x}$$

What does the number 0.8 represent?
(A) Every foot of the pipe removes 20% of the pollutant. 
(B) Every foot of the pipe removes 80% of the pollutant. 
(C) The original amount of pollutant present in the fuel was 80 tons.
(D) The original amount of pollutant present in the fuel was 20 tons.

anonymous · Answer

Can someone plz help me ASAP? @Data_LG2 @DanJS @One098 @sammixboo @arabpride

arabpride · Answer

0.8 is that same as 8/10 [eight tenths] or can be expressed by 80%
~So which of your options makes the most sense in matching that^

anonymous · Answer

B?

arabpride · Answer

I think so c:
-makes the most sense to me
Hope im right~

anonymous · Answer

I was actually thinking that it could have been A. But can you clarify with someone else tho, plz?

arabpride · Answer

I'm not 100% sure myself tbh, but why does A.) make sense to you? :]

anonymous · Answer

i dont know but 100% - 80% = 20% meaning 0.2. It just happens to be that I would always have to subtract the number enclosed in parentheses by 100%.

anonymous · Answer

@pooja195 @PRAETORIAN.10 Can u help or clarify?

pooja195 · Answer

After every foot, 0.8 or 80% of the pollutants will remain, so how much was removed?

pooja195 · Answer

f(x) = 10(0.8)x

anonymous · Answer

20%

anonymous · Answer

So it is B? @pooja195

pooja195 · Answer

no its A

anonymous · Answer

ok thnx

danjs · Answer

The original amount is found at x = 0, a base raised to the zero power is 1

y(0) = 10(0.8)^0  = 10*1  = 10

The initial amount was 10, that crosses off choices C and D

danjs · Answer

sorry was gone for a few minutes

danjs · Answer

every time you increase x by 1, the power on 80/100 increases by 1

at x = 1 , you have 10(8/10)

at x=2, you have 10(64/100)

x= 3,  10(4096/10000)

The fractions are becoming smaller by 20 percent of the last fraction each time

danjs · Answer

IE  y = (1/2)^x     for increasing x

1/2 ....1/4.....1/8....1/16.....1/32....1/64......1/2^n     for n=1,2,3,4,5.....

danjs · Answer

remember the base in that other problem that was between 0 and 1, always got closer and closer to zero as you went on down the x axis... same thing in this problem... 
k im done now  :)

anonymous · Answer

thank you  ; )

danjs · Answer

welcome