Bacteria X has a growth rate of 160 % per hour. Some amount of bacteria X are accidentally introduced into some egg salad. Two hours after contamination, there were 45,000 bacteria X in the egg salad.

Find the initial number of bacteria X introduced into the egg salad:

Estimate the number of bacteria in the food 3 hours after contamination.

initial number:  17,773

3 hours after contamination: 72,798  

Step-by-step explanation:

We know that the growth rate is 160% (or 1.6 in decimal form)

This means that if we start with a quantity A initially, after one hour we will have a quantity A*1.6 of bacteria.

After another hour, we will have a quantity (A*1.6)*1.6 = A*1.6^2 of bacteria.

Then we can model this with an exponential equation:

B(t) = A*1.6^t

where t is the time in hours.

We know that when t = 2, we have:

45,000 = A*1.6^2

Here we can solve it for A, which is the initial number of bacteria X.

A = 45,500/(1.6^2) = 17,773,4

That we can round down, because we need whole numbers, so the initial number of bacteria X in the egg salad is A = 17,773

If we want to find the number of bacteria 3 hours after the contamination, we need to use t = 3.

B(t) = 17,773*1.6^t

B(3) = 17,773*1.6^3 = 72,798.2

That again, we need to round to the next whole number, so we round down.

B(3) = 72,798  

answer:

payment just for service  

→

$

87.12

payment for service including tax

→

$

94.09

explanation:

service only with 20% tip  

→

$

72.6

(

1

+

20

100

)

=

$

87.12

in the opening of the question the word 'service' is associated only with the pretax value.

the closing part of the question asks: how much did she pay for the  

service

−−−−−−  

so technically the answer is  

→

$

72.6

(

1

+

20

100

)

=

$

87.12

however, the intention of the question provider may have been that your answer is to be  

$

87.12

(

1

+

8

100

)

=

$

94.09

to 2 decimal places.

'

payment just for service  

→

$

87.12

payment for service including tax

→

$

94.09

tony b

mar 21, 2017

answer:

trying to explain it another way

explanation:

service charge  

.

→

$

72.60

20% tip  

20

100

×

$

72.60

=

$

14.52

−−−−−−  

←

add

$

87.12

tax  

8

100

×

$

87.12

=

$

6.97

−−−−−  

←

add

$

94.09

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i would need to see the dot plot : )