Ales read 1/3 of a book Monday. 28 pages Tuesday . still has 1/3 left to read. how many pages in book

there are 84 pages in the book.

Step-by-step explanation:

let's call the pages in the book b.

1/3b + 1/3b + 28 = b

2/3b + 28 = b

subtract 2/3b from both sides of the equation

2/3b - 2/3b + 28 = b - 2/3b

28 = b - 2/3b

28 = b/3

multiply both sides of the equation by 3

28 * 3 = b/3 * 3

28 * 3 = b

84 = b

The book has 84 pages

Step-by-step explanation:

Equations

Let's make:

x = number of pages of the book

Alex read 1/3x of the book on Monday, 28 pages on Tuesday, and still has 1/3x left to read. The sum of all these portions add up to the number of pages of the book, thus:

Multiplying by 3:

Simplifying:

x = 84

The book has 84 pages

irst, find the z score of a score of 80. this is given by the formula z = (x-u)/o, where x is the score, u is the mean, and o is the standard deviation. this gives

z = (80-78)/12 = 1/6 = .1667

now, find what percentile a z score of 1/6 correlates to in the normal distribution.

a z score of 1/6 = .1667 is equivalent to the 56.36th percentile of the distribution. so the probability a score is over this is 1-.5636 = .4364

the mean of a sample mean is equal to the original mean. however, the standard deviation of a sample mean is equal to the original standard deviation divided by the square root of n (sample size). so the new standard deviation is 12/sqrt(16) = 3.

the new z score is 80-78/3 = 2/3 = .667. this is equivalent to the 74.86th percentile. so the probability that the mean will be greater than this score is 1-.7486 = .2514.