Raul received a score of 77 on a history test for which the class mean was 70 with a standard deviation of 6. he received a score of 79 on a biology test for which the class mean was 70 with standard deviation 4. on which test did he do better relative to the rest of the class?

He did better on biology test.

Step-by-step explanation:

For comparing the scores we need to find z-scores for both subjects,

We know that,

z-score or standard score for x is,

Where, is mean,

is standard deviation,

In history test,

Thus, the z-score would be,

In biology test,

,

Thus, the z-score would be,

∵

Hence, he did better on biology test.

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)