Answer:
10
Step-by-step explanation
The earthquake measures 6.4 on the Richter scale which struck Japan in Jullu 2007 and caused and extensive damage. Earlier that year, a minor earthquake measuring 3.1 in the Richter scale has stroked in parts of Pennsylvania.
Fomular:
The magnitude of an earthquake is M log(I/S)
where I donates the intensity of the earthquake and S be the intensity of the standard earthquake.
Calculation:
Consider that M1 be the magnitude Japanese earthquake and M2 be the magnitude of the Pennsylvania earthquake and L1 be the intensity of the Japanese earthquake and L2 the intensity of the Pennsylvania earthquake.
Here the magnitude of the Japanese earthquake is M1 = 6.14 and the magnitude of the Pennsylvania is M2 = 3.1
By the use of magnitude of the earthquake fomular M = log I1/S, the intensity of the Japanese earthquake is calculated as follows .
M1 = log I1/S
I1/s = 10
According to Sturge's rule, number of classes or bins recommended to construct a frequency distribution is k ≈ 7
Sturge's Rule: There are no hard and fast guidelines for the size of a class interval or bin when building a frequency distribution table. However, Sturge's rule offers advice on how many intervals one can make if one is genuinely unable to choose a class width. Sturge's rule advises that the class interval number be for a set of n observations.
Given,
n = 66
We know that,
According to Sturge's rule, the optimal number of class intervals can be determined by using the equation:

Here, n is equal to 66 and by substituting the value to the equation we get:

k = 7.0444
k ≈ 7
Learn more about Sturge's rule here: brainly.com/question/28184369
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The answer is .4x because -3.4x+3.8x
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