The reason fractions need a common denominator before adding or subtracting is so that the numbers of pieces you are adding/subtracting are all the same size. Note that the numerator of a fraction just tells you how many pieces you have of that size.
Answer:
27cm^2
Explanation:
3 x 9 = 27
To evaluate the probability that a randomly selected day will be between 28 and 34 minutes we proceed as follows:
P(28<x<34)
First we evaluate the z-score for the above values:
z=(x-σ)/μ
μ=26.7
σ=5.1
when:
x=28
z=(28-26.7)/5.1
z=0.26
P(z<0.26)=0.6026
when x=34
z=(34-26.7)/5.1
z=1.43
P(z<1.43)=0.9236
hence:
P(28<x<34)=0.9236-0.6026=0.321~32.1%
