If x/y = 1/9 and y/z = 9/8 then z/x = ?

a) 1/648
b) 1/8
c) 8/81
d) 81/8
e) 8

could you explain how to do this.

What is the mean of the sum of positive single digit integers

1. draw a histogram from all the data. starting at the bottom row, for each set of 10 flips, place an "x" in the column corresponding to the number of heads that set produced. your histogram should look similar to the example below: 2. calculate the mean and standard deviation. mean = standard deviation = 3. calculate the percent of the data that is within 1, 2, and 3 standard deviations of the mean. within 1 standard deviation = % within 2 standard deviations = % within 3 standard deviations = % 4. compare your results to a normal distribution. interpret any differences.

Write a general formula to describe the variation: x varies directly with y