A petri dish is simply a circle; thus, we use the formula of the area of the circle which is <span>πr^2.
Given r = 40 mm
A = </span>π(40)^2 = <span>5026.55 sq. mm
</span>
Population density = bacteria count / area
PD = 2,100 / <span>5026.55
PD = </span><span>0.417782 bacteria / mm sq.
Therefore, the answer is approximately 0.418 </span><span>bacteria per square millimeter.</span>
Answer:
≥≤ are used when the number is less/greater or equal than some thing.
>< are used when a number is strictly less/greater than some thing.
1) a number x is less than 0 or at least 3
A number x is less than 0 is written as: x < 0.
x is at least 3 is written as: x ≥ 3.
Then we can write the statement as:
x < 0 ∨ x ≥ 3.
where ∨ means "or"
2) a number x is less than or equal to 4 and greater than -1
x less than or equal to 4 is written as: x ≤ 4
x is greater than -1 is written as: x > - 1.
We can write the statement as:
-1 < x ≤ 4
3) a number x is less than 8 and greater than or equal to 5
x is less than 8 is written as: x < 8
x is greater than or equal to 5 is written as: x ≥ 5.
Then the statement can be written as:
5 ≤ x < 8,
Answer:
(9,3)
Step-by-step explanation:
4(.25x + .5y = 3.75) → x + 2y = 15
(4x – 8y = 12) → x – 2y = 3
2x = 18
Divide both sides by 2
x = 9
Substitute x = 9 into x + 2y = 15
9 + 2y = 15
Subtract 9 from both sides
2y = 6
Divide both sides by 2
y = 3
Solution
(9, 3)
Angles c and e are vertical
Answer: 3.751*10^18kg
Step-by-step explanation:
δ =619.09−0.000097p....equa1 where p (the distance from the center of the earth) is measured in meters and δ is measured in kilograms per cubic meter.
Calculating the density of air at 5km above earth surface
P = 5000m + 6370000m = 6.375*10^6m
δ = 619.09 -(.000097* 6.375*10^6)
δ = 0.715kg/m^3 = density
Since Mass = density*volume...equ2
To calculate volume of air around the spherical earth at height 5km
V = (4/3 pai R^3) - (4/3pai r^3) ...equation 3 where R =6.375*10^6m, r = 6.37*10^6
Substituting R and r in equation 2 to solve for volume of air
V = 1.085*10^21 - 1.08*10^21
V = 5.25*10^18m^3
Substituting δ and V into equation 2 to solve for mass of air
M = 0.715 * (5.25*10^18)
M = 3.751*10^18kg
