Athena bought x boxes of cookies to bring to a party. Each box contains 10 cookies. She decides to keep two boxes for herself. S
1 answer:
Given parameters:
Number of boxes Athena bought for the party = x
Number of cookies per box = 10
Number of cookies she brought to the party = 70
Number removed = 2 boxes
Unknown:
Equation of the number of boxes = ?
Solution:
1 box of cookies contains 10 cookies
If Athena, removed 2 boxes, in those two boxes, we have 20 cookies
Total number of cookies = 70 + 20 = 90 cookies;
So;
x =
Therefore;
x = boxes
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The first step is to identify the order in which the equation must be solved, by following PEMDAS (you might know it as BEDMAS):
Parenthesis (or Brackets)
Exponents
Multiplication and Division
Addition and Subtraction
My advice would be to add parenthesis, following these rules, if you are not very good at finding them immediately by sight.
So:
We check our answer:
We are right!
So, .
Answer:
- P(t) = 100·2.3^t
- 529 after 2 hours
- 441 per hour, rate of growth at 2 hours
- 5.5 hours to reach 10,000
Step-by-step explanation:
It often works well to write an exponential expression as ...
value = (initial value)×(growth factor)^(t/(growth period))
(a) Here, the growth factor for the bacteria is given as 230/100 = 2.3 in a period of 1 hour. The initial number is 100, so we can write the pupulation function as ...
P(t) = 100·2.3^t
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(b) P(2) = 100·2.3^2 = 529 . . . number after 2 hours
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(c) P'(t) = ln(2.3)P(t) ≈ 83.2909·2.3^t
P'(2) = 83.2909·2.3^2 ≈ 441 . . . bacteria per hour
__
(d) We want to find t such that ...
P(t) = 10000
100·2.3^t = 10000 . . . substitute for P(t)
2.3^t = 100 . . . . . . . . divide by 100
t·log(2.3) = log(100)
t = 2/log(2.3) ≈ 5.5 . . . hours until the population reaches 10,000
