45mph is the answer if you do the math right
Answer:

Explanation:
We know that the frequency of the nth harmonic is given by
, where
is the fundamental harmonic. Since we have the values of two consecutive frequencies, we can do:

Which for our values means (we do not need the value of <em>n</em>, that is, which harmonics are the frequencies given):

Now we turn to the formula for the vibration frequency of a string (for the fundamental harmonic):

So the tension is:

Which for our values is:

Answer:
5 hours
Explanation:
Let the required time be x hours. The time will be the same for both cars.
The cars will cover different distances because they are travelling at different speeds.
<em>D=S×T
</em>
The distance travelled by the slower car = 50×x miles.
The distance travelled by the faster car = 58×x miles.
The two distances differ by 40 miles.
58x−50x=40
8x=40
x=5 hours
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A second method:
The difference in the distances is 40 miles
The difference in the speeds is #8mph.
The time to make up the 40 miles=
=5 hours
This behavior helps Betty in <u>intellectual </u>development.