The pH of a substance added to a citrate buffer, y, depending on the ratio of citric acid to sodium citrate, x, can be modeled using the equation y = 6.4 – log x. If the pH of the substance is 6.5, what is the ratio of citric acid to sodium citrate? A.0.79
B. 1.26
C. 5.59
D.7.20

It's A

Yes it's A. 0.79

Step-by-step explanation:

You plug in 6.5 into the y-value since it asks to find the ratio,x, if the pHis 6.5. Then you can solve using a calculator to get 0.79432, or 0.79

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

85.560%

step-by-step explanation:

conditional probability is defined as:

p(a|b) = p(a∩b) / p(b)

in other words, the probability that a occurs, given that b has occurred = the probability that both a and b occur / the probability that b occurs.

in this example:

p(turns 64 | turns 44) = p(turns 64 & turns 44) / p(turns 44).

if someone turns 64, they must have already turned 44, so:

p(turns 64 | turns 44) = p(turns 64) / p(turns 44)

on page 42, we see that of the original 100,000, 94944 turn 44, and 81234 turn 64.   therefore:

p(turns 64 | turns 44) = 81234 / 94944

p(turns 64 | turns 44) = 0.85560