For a read-a-thon, jay and odhràn each started reading a book at the same time and continued reading for several hours. jay's book had 278 pages, and he read 55 pages per hour. odhràn's book had 238 pages, and he read 45 pages per hour. after how many hours did they have the same number of pages left, and how many pages were left?

4 hours

Step-by-step explanation:

Let after x hours both have equal number of left pages.

Since, Jay's book had 278 pages, and he read 55 pages per hour.

Thus, after x hours the number of pages he read = 55 x

⇒ After x hours the pages he has left = 278 - 55x

Similarly, Odhràn's book had 238 pages, and he read 45 pages per hour.

⇒ After x hours the pages he has left = 238 - 45x

Therefore, we can write,

278 - 55 x = 238 - 45 x

⇒ 278 - 55 x + 45 x = 238

⇒ 278 - 10 x = 238

⇒ - 10 x = 238 - 278

⇒ - 10 x  = - 40

⇒ x = 4

Hence, after 4 hours they have same number of pages left.

They will read for 4 hours and they will both have 58 pages left

This is correct because it was right in khan academy!

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;