Let the slower train's velocity be x-21
Let the faster train's velocity be x
We know that the approach speed is the sum of both speeds, so x+x -21= 2x-21.
The approach rate is given by Distance/time = 471/3 = 157mpH
x+x-21=157
2x=157+21
2x=178
x=89mph
The slower train is travelling 89-21 = 68mph
The faster train is travelling 89mph.
Answer: I believe the correct answer is option D.
Answer:
1. T test for independent means
2. T test for dependent means
3. T test for dependent means
Step-by-step explanation:
In number 1, the two groups are unrelated. The first group has 25 subjects and they're all unemployed. The second group has 24 subjects and their employment status is not stated and might not be the same all through. Also, the first group is receiving a new type of job skills program while the second group is taking the standard job skills program.
- The groups in the experiment are unrelated
- The tests in the research are unrelated
- The purpose of the research is unreasonable - the researcher seeks to measure how well all 49 subjects perform on 'a' job skills test! No comparison between the scores or mean scores of the two groups.
In number 2, the researcher uses the same subjects and also measures the same variable but twice. This is a good example of a study where the t test for dependent means can be taken. Same applies in case 3.
Let J = rate of jet in still airLet W = rate of wind Distance formula: d = rt / r = d/t Flying against the wind the jet flies at a rate of J - W = 1860 miles/3 hours = 620 miles per hourFlying with the wind the jet flies at a rate of J+W = 9180 miles/9 hours = 1020 miles per hour The average of these 2 rate is the speed of the jet in still air J = (620+1020)/2 = 820 miles per hour J - W = 620
820 - W = 620
W = 820 - 620 = 200 miles per hour The jet in still air flies at a rate of 820 mph(miles per hour)The wind speed is 200 mph(miles per hour)
