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
#SPJ4
To remove the parentheses, you just distribute.
So, it will become 3ax + 3b^2 - 3c +2. I don't think there is any like term in this expression.
We have 4(x^2 - 2x + 4) - 7 = 4x^2 - 8x + 16 - 7 = 4x^2 - 8x + 9;
So, 4x^2 - 8x + 9 = <span>ax^2+bx+c
;
The value of b is -8.</span>
Answer: #20, x = 3
#21, x = 1/2
Step-by-step explanation:
#20) x + 4 + x + 2+ x + 5 = x + 3 +x+3+x+1+x+1
3x + 11 = 4x + 8
<u>-3x -3x</u>
11= x + 8
<u> - 8 - 8</u>
3 = x
#21) 12x(5) = 6x + 9 + x + 10 + x + 7
60x =8x + 26
<u> -8x -8x</u>
52x = 26
divide both sides by 52
x = 1/2