Step-by-step explanation:
Rate of growth equals 420/100 = 4.2 times per hour
So after t=three hours,
size of culture = 100*(4.2)^t = 100*4.2^3=7408.8 bacteria,
round to nearest unit 7409 bacteria after three hours (after initial size of 100).
Answer:
- 6 2/3 qt 80%
- 13 1/3 qt 20%
Step-by-step explanation:
It is often convenient to solve a mixture problem by letting a variable represent the quantity of the higher-concentration contributor to the mix.
__
We can let x represent the number of quarts of 80% solution needed. Then (20-x) is the number of quarts of 20% solution needed. The amount of salt in the final mix is ...
0.80x +0.20(20-x) = 0.40(20)
0.60x = 0.20(20) . . . . . . . . subtract 0.20(20) and simplify
x = 20/3 = 6 2/3 . . . . . . . . . divide by 0.60; quarts of 80% solution
(20 -x) = 13 1/3 . . . . . . . . . . amount of 20% solution needed
The teacher should mix 6 2/3 quarts of 80% solution with 13 1/3 quarts of 20% solution.
Answer:
Step-by-step explanation:
To isolate r, we're going to need to do some algebraic manipulation.
Multiply both sides by r:
Divide both sides by a:
Hope this helps!
Answer:
Step-by-step explanation:
Therefore, the coefficient of 
is .
Answer:
The sidewalk is 2 feet wide
Step-by-step explanation:
The area of the sidewalk is given as 80 square feet
The length and width of pool
including side walks will be;
10 + 2x and 6 + 2x
To get the area of the side walk
That will be area of total minus area of the pool
That will be ;
(10 + 2x)(6 + 2x) - 10(6) = 80
60 + 12x + 20x + 4x^2 - 60 = 80
4x^2 + 32x -80 = 0
x^2 + 8x -20
x^2 + 10x - 2x - 20 = 0
x(x + 10) -2(x + 10) = 0
(x-2)(x + 10) = 0
x = 2 or -10
since width cannot be negative;
The sidewalk is 2 feet wide
