A store sells hardcover books for $8 and paperback books for $5. You buy 9 books, represented by the equation x + y = 9, where x is the number of hardcover books and y is the number of paperback books. The equation 8x + 5y = 57 represents the total cost. How many of each type of book did you buy?

answer: i think the answer is etheir c or d but i don't know which one but have a good day!

step-by-step explanation:

d. 24+-0.114

step-by-step explanation:

the question requires us to calculate the approximate 95% confidence interval for the mean number of ounces of ketchup per bottle in the sample given the following statistics;

sample mean = 24

standard deviation, σ = 0.4

sample size , n = 49

the confidence interval for a population mean is calculated using the formula;

sample mean ± z-score*(σ/sqrt(n))

the z-score associated with a 95% confidence interval, from the standard normal tables, is;

1.96

substituting these values into the formula;

24 ± 1.96*(0.4/7)

= 24 ± 0.112

from the alternatives given, choice d is closest to the above expression;

the answer is 13 cm

the arc length is found by finding the circumference of the full circle (2xpixradius) and then dividing by 4 to find just one quarter of the circle (90 degrees).