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Answer: it will take a combined rate of 2.67 hours
Step-by-step explanation:
Father can do the job on the farm in 6 hours. This means that the father's unit rate of working will be 1/6
The older son can do it in 8 hours. This means that the older son's rate of working will be 1/8
The younger son can do same job in 12 hours. This means that the younger son's working rate is 1/12
When they work together, they will be working simultaneously. It means that their unit rates are additive. The combined unit rates will be
1/6 + 1/8 + 1/12 = (20 + 15 + 10)/120
45/120
Assuming it takes t hours for them to complete the work while doing it together. Their combined unit rate will be 1/t
45/120 = 1/t
45t = 120
t = 120/45 = 2.67 hours
Answer:
The 95% confidence interval based on this sample is =
[6.41, 7.79]
Step-by-step explanation:
The formula for Confidence Interval =
Mean ± z × standard deviation/√n
Sample mean = 7.1 hours
Standard deviation = 5 hours
n = 200 students
z = 95% confidence interval z score
= 1.96
C.I = 7.1 ± 1.96 × 5/√200
C.I = 7.1 ± 0.693
Hence, Confidence Interval
= 7.1 - 0.693
= 6.407
Approximately = 6.41
= 7.1 + 0.693
= 7.793
Approximately = 7.79
Therefore, the 95% confidence interval based on this sample is
[6.41, 7.79]
She would run 15 km in an hour and a half and 25 km in 2 1/2 hours
Answer:
Its C
Step-by-step explanation:
