The answer to the question
Answer:
45 minutes
Step-by-step explanation:
At 30 mph for 1/4 hour, Peter has a 7.5 mile head start. After he leaves, Mitchell closes that gap at the rate of 40-30 = 10 miles per hour. It will take him ...
t = d/s
t = (7.5 mi)/(10 mi/h) = 0.75 h
to catch Peter.
Mitchell will catch Peter in 45 minutes.
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<em>Alternate Solution</em>
Another way to look at it is that Mitchell's 10 mph advantage is 1/3 of Peter's speed, so it will take 1/(1/3) = 3 times the period of Peter's head start:
3 × 15 minutes = 45 minutes . . . for Mitchell to catch Peter
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You can write equations involving time and distance and see where the distances traveled become the same. You need to be careful choosing the time reference, since you're concerned with Mitchell's travel time. I personally prefer to work "head start" problems by considering the differences in time and speed, as above. This is where you end up using the equations approach, anyway.
Answer: 256
Step-by-step explanation:
The maximum weight on a roller coaster is 400 pounds (Max = 400).
If your friend weighs 120 pounds (y = 120), what is the most you can weigh so you can ride together (x + y < 400).
x + 120 <_ 400.
y = 120
Subtract 120 from both sides.
x <_ 280.
You can weigh at most 280 pounds (x <_ 280).
I hope this helps!
