The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20.according to the standard deviation rule, in a semester, most (95%) of the students spent on textbooks: a. between 215 and 255 dollars. b. between 195 and 275 dollars. c. between 175 and 295 dollars. d. less than 215 dollars or more than 255 dollars. e. above 235 dollars.

b. between 195 and 275 dollars.

Step-by-step explanation:

The standard deviation rule, or the 68-95-99.7 rule, states that, for a normally distributed random variable X:

68% of the measures are within 1 standard deviation of the mean

95% of the measures are within 2 standard deviations of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean 235, standard deviation 20.

According to the Standard Deviation Rule, in a semester, most (95%) of the students spent on textbooks:

Between 235 - 2*20 = 195 dollars and 235 + 2*20 = 275 dollars.

So the correct answer is:

b. between 195 and 275 dollars.

b. between 195 and 275 dollars

Step-by-step explanation:

The Standard Deviation Rule states that for a normal distribution, nearly all of the data will fall within three standard deviations of the mean . The empirical rule is further illustrated below

68% of data falls within the first standard deviation from the mean.

95% fall within two standard deviations.

99.7% fall within three standard deviations.

From the information given, the mean is $235 and the standard deviation is $20.

95% of the amount spent by students on text books would fall within two standard deviations.

2 standard deviations = 2 × 20 = 40

235 - 40 = 195

235 + 40 = 275

Therefore, the amount spent is between between 195 and 275 dollars.

< coa = 150 ( given)

as ba and bc are tangents

so oc and oa is perpendicular to cb and ab respectively because in circle normal passes through centre

so in quadrilateral oabc

< coa + < oab + < ocb + < abc = 360

150 +90+90 + < abc = 360

330 + < abc = 360

< abc = 360 -330 = 30

so < abc = 30

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