Hello there!
Let's review the information we're given, and the question that's being asked.
We are given that there is a plane which flies at 450 miles per hour. ("A jet plane flies at 450 miles per hour.)
We can also see that the question is how far it would travel in 18 minutes most likely assuming it to be going the same speed. ("How far does it travel in 18 minutes?")
Now, let's connect these two parts of information we're given, by asking a few questions ourselves.
First: How can we answer the question with the information given?
To answer this question, we can break it down into smaller questions. Here is one to start off with.
- How does 450 mph and 18 minutes relate?
Let's answer it. How does 450 mph and 18 minutes relate?
One of the most important things to note for this is one hour = 60 minutes. Therefore, we can see these two are related as you can convert either mph or minutes to miles per minute or hours (respectively).
Now I'm going to do just that by converting 18 minutes to an hour:
If you know one hour = 60 minutes, what would you do to make the right side 18 minutes? I would personally multiply both sides by 18/60, making the left side 3/10 (18/60 simplified is 3/10) of an hour, and the right 18 minutes (because 18/60 * 60 = 18)
Alright. So now we know that 18 minutes is equal to 3/10th of an hour. Since the units now match (450 miles per hour and 3/10th of an hour), we can relate them.
Mph is miles per hour, so how many miles traveled in an hour. In an hour. Does that sound familiar? We do have a number with the unit of an hour, 3/10th of an hour.
We therefore see the answer to the question how does 450 mph and 18 minutes relate is, well, another question?
From that, we can get the question of, how far does a jet plane travel going at the rate of 450 mph for 3/10th of an hour?
Since we have defined what MPH is (how many miles traveled in an hour), we can therefore figure out how to calculate that question with math.
The correct method to calculate would be to multiply 3/10 and 450 together. Why?
Multiplication is essentially adding something a certain number of times. For example, multiplying 2 by 3 is adding 2 three times, to get 6.
Now, if you want to find 3/10th of 450, you would multiply it as that would result in 3/10th of 450, as you're adding 3/10th of 450. (as for lack of better phrasing.)
Now, let's calculate.
(Very vague explanation as to why, if it interests you you can think about it more personally.)
3/10 * 450 = 135 miles
We get our answer of 135 miles.
Hope this helped!