The sister catches up Jeff after 2 hours
Step-by-step explanation:
We can write Jeff's position and his sister position at time t using the following expressions:
- Jeff position:

where:
7 is the initial position of Jeff when his sister sarts chasing him
2.5 is Jeff's velocity (in miles/hour), so its position increases by 2.5 miles for each hour
t is the time measured in hours
- Sister position:

where
6 is the sister velocity (her position increases by 6 miles for every hour)
t is the time measured in hours
The sister catches up Jeff when the two positions are equal, so

And solving for t,

So, the sister catches Jeff after 2 hours.
Learn more about speed:
brainly.com/question/8893949
#LearnwithBrainly
Answer:
140yd2
Step-by-step explanation:
That's all the square roots of the form 5.xxxx. The numbers start at 5² and end at 6²-1.
So that's 6² - 5² = 11 numbers. We can list them:
25,26,27,28,29,30,31,32,33,34,35
Answer: 11