Speed/Distance/Time + Fuel Consumption

[RCAF91]

To begin, this isn't "homework" I'm preparing to take a test that will have this types of questions and I wanted to see if I could get any insight and strategies to be able to solve these as quickly and accurately as possible; even mentally if there are any methods (for more complicated types)

So, obviously we've got our formulas:

Distance = Speed / Time
Speed = Distance / Time
Time = Distance / Speed

Also breaking up "chunks of time" in an hour

2 of 30 mins
3 of 20 mins
4 of 15 mins
5 of 12 mins
10 of 6 mins
12 of 5 mins
15 of 4 mins
20 of 3 mins
30 of 2 mins


An example of an easy question to do mentally would be:

Speed of 24 mph, how far would you travel in 1 hour 15 minutes?
0.25 of 24 is 6. Therefore, 24+6 = 30 miles


I'm wondering if anyone knows the quickest most efficient way to solving questions such as:

What speed covers 18 miles in 54 minutes

And if there's a simple way to do it mentally?

I appreciate your replies!

This site has some sample tests including the fuel consumption questions too.
Speed Distance Time | OASC: RAF Officer and Aircrew Selection Centre

Here's a fuel consumption question that I'm wondering what the quickest method to solve would be:

You travel 111 miles. How much fuel will you need if you burn 36 kgs per hour, and are travelling at 148 mph?

 

[stapel]

To quote from a reply to another instance of this posting:

So, obviously we've got our formulas:

Distance = Speed / Time

No: distance equals rate ("speed") TIMES time (not divided by). You can learn more here.

I'm wondering if anyone knows the quickest most efficient way to solving questions such as:

What speed covers 18 miles in 54 minutes

Plug into the formula d = rt:

18 miles = r(54/60 hr) = r(9/10 hr)

18 = (9/10)r

Then solve:

(18)(10/9) = r

Simplify to get the answer in miles per hour.

And if there's a simple way to do it mentally?

Unless the numbers are really easy, probably not. Working by hand and with a calculator is the regular way.

You travel 111 miles. How much fuel will you need if you burn 36 kgs per hour, and are travelling at 148 mph?

Use d = rt to find the time t for d = 111 and r = 148. Then multiply the hours by the kgs-per-hour to get the kgs. If you need to learn how to keep track of the units, try here.

 

[Ishuda]

To begin, this isn't "homework" I'm preparing to take a test that will have this types of questions and I wanted to see if I could get any insight and strategies to be able to solve these as quickly and accurately as possible; even mentally if there are any methods (for more complicated types)

So, obviously we've got our formulas:

Distance = Speed / Time
Speed = Distance / Time
Time = Distance / Speed

Also breaking up "chunks of time" in an hour

2 of 30 mins
3 of 20 mins
4 of 15 mins
5 of 12 mins
10 of 6 mins
12 of 5 mins
15 of 4 mins
20 of 3 mins
30 of 2 mins


An example of an easy question to do mentally would be:

Speed of 24 mph, how far would you travel in 1 hour 15 minutes?
0.25 of 24 is 6. Therefore, 24+6 = 30 miles


I'm wondering if anyone knows the quickest most efficient way to solving questions such as:

What speed covers 18 miles in 54 minutes

And if there's a simple way to do it mentally?

I appreciate your replies!

This site has some sample tests including the fuel consumption questions too.
Speed Distance Time | OASC: RAF Officer and Aircrew Selection Centre

Here's a fuel consumption question that I'm wondering what the quickest method to solve would be:

You travel 111 miles. How much fuel will you need if you burn 36 kgs per hour, and are travelling at 148 mph?

It depends on the problem and possibly to some extent on the type of test. For example your question of "What speed covers 18 miles in 54 minutes". I immediately think that I need another 6 minutes to make it an hour, that means 10%, so 18 divided by 90% is 20mph. Quick check 20 mph is 1/3mile min times 6 min is 2 miles. Of course this happens faster than writing about it.

For "You travel 111 miles. How much fuel will you need if you burn 36 kgs per hour, and are travelling at 148 mph?" Should be (order of magnitude) about 25. If not close enough then 148 is 150 minus about a percent, so 2/3 (=1/1.5) times 111=222/3=74 +1% is about 75 times 36 is 2250+450 = 2700, so around 27kgs. which should be good for multiple choice.