The correct option is "d".
Given that L = 0.8T²
length of pendulum = 30ft
L= 0.8T²
30 = 0.8T²
T² = 30 / 0.8
T² = 37.5
T = √37.5 = 6.1 seconds
<span>So, 6.1 is the closest to the period in seconds for a pendulum that is 30 ft long.</span>
I’ve attached my work below
Hope it helps!!
we know that
The formula of the surface area of the cone is equal to

where
SA is the surface area
r is the radius of the cone
l is the slant height
in this problem we have

Solve the formula for l

substitute the values

therefore
<u>the answer is</u>
The slant height is 
Here is the equation:

Since both decimals are negative, the answer will be positive.
- Negative times Negative = Positive
Divide both sides by -3.9 to leave the variable alone:

r is equal to 4 → r = 4
Answer:
r = 2.55
Step-by-step explanation:
The formula for finding the radius of a circle using the area is r = √A/π
with the r being the radius. the A being the area, and the π being pi (we'll use 3.14).
So the equation should look like this:
r = √(20.4/3.14)
Find the quotient of 20.4/3.14 and round to the nearest tenth
r = √6.5
Find the square root and round to the nearest hundredth
r = 2.55