speed time distance calculations

[thrila]

Hi i'm off for pilot aptitude testing and i'm struggling with some aspects of speed time distance.  I was hoping for some tips, i'm ok at simple questions and i've been practising, however some questions either stump me ot take me several minutes to do. 

Here's a few examples at the ones i struggle with:

travelling at 135mph for 16 minutes- how far have i travelled.

travelling at 95mph, what time would it take to travel 38 miles.

travelling 132mph, what time would it take to travel 110 miles.

and even something simple such as this can take me a while: i travel 3 miles in 9 minutes- what speed am i traveling at.


I'm doing these without pen and paper.  Any tips would be very handy, thanks

[Dowding]

Simple S = vt type stuff, but I'm lazy and would need a calculator - presumeably you don't get one? None of those problems involve easy fractions which could be done quickly in my head (and I hold a degree in physics).

[john9001]

Distance  =  Speed  x  Time
Speed  =  Distance  ÷  Time
Time  =  Distance  ÷  Speed

there used to be a circular slide rule that was used for that, we called it a "is-was".

[AWMac]

This pretty much should simplify your problem.
 

Mac

[kamilyun]

Hi i'm off for pilot aptitude testing and i'm struggling with some aspects of speed time distance.  I was hoping for some tips, i'm ok at simple questions and i've been practising, however some questions either stump me ot take me several minutes to do. 

Here's a few examples at the ones i struggle with:

travelling at 135mph for 16 minutes- how far have i travelled.

travelling at 95mph, what time would it take to travel 38 miles.

travelling 132mph, what time would it take to travel 110 miles.

and even something simple such as this can take me a while: i travel 3 miles in 9 minutes- what speed am i traveling at.


I'm doing these without pen and paper.  Any tips would be very handy, thanks

Are these questions on a practice test or something?  In my experience, if they ask you to do it without pen and paper, it usually boils down to some simple fractions.

For example, 135 mph for 16 minutes--In my head works out like this: 16/60 = 8/30 = 4/15 hours.  135 is divisible by 3 and by 5 so must be divisible by 15.  It is = to 9 x 15.  So you're left with 9 x 4 = 36 miles.

Even simpler is that 16 is about 1/4 of an hour, so 1/4 of 135 is about 34 miles (4 into 13 = 3, 4 into 15 is about 4).

Might not work for you, but that's how I work these types of fraction problems in my head.  Reduce to simplest whole numbers, then divide or multiply.

Good luck <S>

[Dux]

Is doing it in your head a requirement? Last I heard they still allow calculators or flight computers.

The magic number is 60... try to get everything to balance with 60. 60 seconds in a minute, 60 minutes in an hour. 60 mph is one mile per minute.

So 135 mph at 16 minutes = roughly 2.25 miles per minute x 16 minutes = 36 miles.

So if you can travel 95 miles in an hour, and 38 miles is slightly more than a third of that, then it takes slightly more than a third of an hour to travel. ~40% (4/10ths) of 60 is 24 minutes.

etc, etc.

Practice it a bit it'll become easier. Do it while you're driving.

ps. I remember reading the story about the Israeli strike on the Osirak reactor. They had the strike planned down to the second, and to make that easier, they used speeds that were multiples of 60... 240, 300, 360. So remember 60.

[Golfer]

[CAP1]

Hi i'm off for pilot aptitude testing and i'm struggling with some aspects of speed time distance.  I was hoping for some tips, i'm ok at simple questions and i've been practising, however some questions either stump me ot take me several minutes to do. 

Here's a few examples at the ones i struggle with:

travelling at 135mph for 16 minutes- how far have i travelled.

travelling at 95mph, what time would it take to travel 38 miles.

travelling 132mph, what time would it take to travel 110 miles.

and even something simple such as this can take me a while: i travel 3 miles in 9 minutes- what speed am i traveling at.


I'm doing these without pen and paper.  Any tips would be very handy, thanks

you're not allowed to use an E6B? i think i was allowed to use one in my written exam, and always have one with me in the cockpit........

[Hap]

r x t = d

[eskimo2]

Thrila,
If you have any doubts or are unsure of your calculations, its wise check your work with a rough estimation.

“travelling at 135mph for 16 minutes- how far have i travelled”
Round 16 minutes to ¼ hour.
Round 135 miles to 140 so that you can easily divide by 4. 
Your answer should be in the ballpark of 35 miles.
If the answers they provide are:
A. 24 miles
B. 36 miles
C. 72 miles
D. 119 miles
You really don’t need to waste your time finding the exact number, just circle B. 36

If the answers they provide are:
A. 32 miles
B. 35 miles
C. 36 miles
D. 38 miles
You’d better find the exact answer.

The actual math on paper simplified:
16 minutes out of 60, is 16/60. 
Reduce it to 4/15
Will 15 easily divide into 135?
Yes, 9 times (it may not jump out at you, but 10x15=150, and 135 is 15 less than 150, so 9x15=135)
All that’s left is 9x4, which is 36.
Is 36 reasonably close to the estimation of 35?  Yes.
Circle 36.

The key to doing this kind of math quickly on paper is reducing and simplifying. 

[SFRT - Frenchy]

Are those Nautical miles or Statute miles. NOt too keen in working MPH with Nautical miles.

If all is asked is approximation, then approximate : 3 miles in 9 minutes close from 3 miles in 10 minutes, (*6 for 60 min) a lil above 18 miles per hour.


135 MPH for 16 min. 16 min is close from a 1/4 of an hour. 135 MPH is 135 SM in an hour rounds to 140 miles, 1/4 of 140 is 35 Miles.

  Exact fuel/distance/time computations in exams always made me laught on how non representative of an actual safety issue it really was. Those are what sunday pilots wanabies strive on to impress their girlfriends. Or frustrated examinors

[Yeager]

x + y = z

x being speed

y being distance

z being the sum total of distance covered by any given speed

[avionix]

Use the godd ole wiz wheel E6B.  They even let you use an electronic version for the tests now.  Cost about $75 but it functions as a calculator as well.  Must have some hard arse FAA inspector.  Had one of those once before.

[Shamus]

They still make those things Golfer?, had one in 1977 

shamus

[Golfer]

Beats me.  Fltplan.com handles all my planning    It can even be used on a PDA