Bill drove to town hall and back. the trip there took 1.5 hours and 2hrs on trip back. if bill's speed there was 12 mph faster than on the way back , find his average speed on the way back.

 36 mph

Step-by-step explanation:

Let s represent the speed on the way back. Time is inversely proportional to speed, so the speed ratios are ...

  (speed going)/(speed coming) = (s+12)/s = 2/1.5 = (time coming back)/(time going there)

  1 +(12/s) = 4/3 . . . . . divide, simplify the ratio

  12/s = 1/3 . . . . . . .  subtract 1

  s = 36 . . . . . . . . .  multiply by 3s

Bill's average speed on the way back was 36 mph.

I sometimes like to think of these problems in terms of "ratio units." We have the speed ratio:

  (s+12)/s = 2/1.5 = 4/3

The difference between s+12 and s is 12 mph, and that corresponds to the difference 4-3 = 1 ratio unit. So 3 ratio units will be 36 mph, corresponding to the value of s. Bill's speed on the way back was 36 mph.

  (48 mph)/(36 mph) = 4/3 . . . . check

step-by-step explanation:

i found the life tables for the year 2012. 

life table of males at age 30. probability of dying between ages x and x+1

total population:  

29–30 . . . . . . . . . . . . 0.001030

30–31 . . . . . . . . . . . . 0.001061

males:  

29–30 . . . . . . . . . . . . 0.001420

30–31 . . . . . . . . . . . . 0.001448

white population

29–30 . . . . . . . . . . . . 0.001005

30–31 . . . . . . . . . . . . 0.001037

white males

29–30 . . . . . . . . . . . . 0.001372

30–31 . . . . . . . . . . . . 0.001399

non hispanic white population

29–30 . . . . . . . . . . . . 0.001083

30–31 . . . . . . . . . . . . 0.001116

non hispanic white males

29–30 . . . . . . . . . . . . 0.001477

30–31 . . . . . . . . . . . . 0.001503

jacob, non hispanic white male. 30 years old.

probability that jacob lives to be 30 years old. 

since the given probabilities are probabilities of dying, i think we simply subtract it from 1 to get the probability of living. we will use the probability of non hispanic white male.

                                          probability of living to be 30 y.o.

29 - 30 : 1 - 0.001477 = 0.998523

30 - 31 : 1 - 0.001503 = 0.998497