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# /sci/ Science & Math

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vector 2013-02-15 22:40:51 No.5533100

[Missing image file: speed.jpg]

Hi /sci/,

This is embarassing but as a compsci post grad I have been recently stumped at doing a verbal Speed Distance Time calculation test for the US Army.

I was wondering if there is any techniques for figuring out the answer easily and effectively.

For example:

What speed covers 11 miles in 3 hours and 40 mins?

Many thanks!

>>
Anonymous 2013-02-15 22:47:26 No.5533114
40/60 = 0.666...
3 + 0.666... = 3.666...

11/3.666...
=~ 3.1

~3.1 Miles/Hour

>>
Anonymous 2013-02-15 22:47:53 No.5533117
>can't solve this
You can't be serious.

11 miles / 3 hours 40 mins
11 miles / 220 mins
1 mile / 20 mins
3 mph

>>
Anonymous 2013-02-15 22:48:53 No.5533120
3 hours 40 minutes = 11/3 hours

>>
vector 2013-02-15 22:53:25 No.5533131
>>5533117

Big surprise to you but I haven't really done stuff like this since school.

>>
Anonymous 2013-02-15 23:00:38 No.5533154
11 miles= 17 702.784 m
3 h + 40 min= 13 200 s
v=ds/dt
v=17 702.784 m/13 200 s
v=1.34 m/s

>>
Anonymous 2013-02-15 23:27:57 No.5533227
>>5533117
I don't think he's saying he can't solve it, he just can't solve it quickly, using his brain more than the paper. People can be good at math despite being bad at mental arithmetic.

for me, If you have to do miles per hour, I'd say 3hr40min is 3 and 1/3 hrs. so you're looking to get 1/3.666 of 11 miles. bring that denominator to an integer, so lets do 3/11 of 11 miles. It's 3. 3 mph.

It's different for some problems though. If you had said 11 miles in 1hr40min, then I just need to take whatever proportion of that time the 40mins takes up, and shave that proportion off the 11. 40 minutes is 2/5 of 1hr40min, so I need to shave off 2/5 of 11. 11-4.4 is 6.6mph.

I'm hoping all my math is right or I'll be embarrassed. Just providing my approach.

>>
Anonymous 2013-02-15 23:33:33 No.5533248
my math is rusty, here's how I'd do it

>miles per hour = distance/time. so,
Velocity = distance/time
d/t = d/t
11mi/3.666h = Xmi/1h
>cross multiply
3.666x = 11
x = 3 miles in one hour

>>
Anonymous 2013-02-15 23:48:43 No.5533292
>>5533227
Good point. Op prolly isn't this bad, but I have dyscalculia - under pressure, I can't even multiply in my head. However, I have a B.S. in Mathematics. I follow the units - If it's miles per hour, divide miles by the hour. Remember to watch out for orders of magnitude.

>>
Anonymous 2013-02-16 00:21:29 No.5533374
Convert minuets to hours using fraction
3:40 = 3 2/3 hours or 11/3 hours
you need how many miles per hour so divide miles by hours
11 / (11/3)
so the know that 11/3 goes into 11, 3 times

>>
Anonymous 2013-02-16 03:44:15 No.5533920
bracket and extrapolate. You are given distance and time, solving for velocity. 3 hours times 3 mph equals 9 miles. (less time-less distance). 3 hours times 4 mph equals 12 miles.(less time-more distance) So answer has to be between 3 and 4 mph. Next calculate the additional fraction of hour (2/3). 2/3 hour times 3 mph equal 2. 9 + 2 equals 11. answer 3mph.

>>
Anonymous 2013-02-16 03:52:17 No.5533941
>>5533100
v=s/t
s=11 miles
t=3hours 40 minutes
v=11miles / 3hours 40minutes is a bit awkward to calculate, let's get that to full hours
40 min = 2/3 hour,
3*40min = 2 hours
v = 33miles / 3*(3 hours 40 minutes)
v = 33miles / (9 hours + 2 hours)
v = 33miles/11hours
v= 3 mph

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