Stupid Basic Maths Question

Lucifer666

all the world needs is me
OP
Member
Joined
Apr 22, 2011
Messages
1,626
Trophies
1
Location
The Fourth Dimension
XP
2,160
Country
United Kingdom
I want to start off by saying that I probably already know the answer to this question from an exercise I didn't even think would exist in my course due to how ridiculously easy it is, but I am beyond sleepy right now and can't force it out of my brain. I'm pulling an all-nighter to finish up some work, and I can no longer think. I've gone mad. I'm aware this is a stupid question.

So I'm given the formula d=0.0065v^2 + 0.75v
a) (Some long useless info here) basically translates into find d when v is 50

What I did:
d=0.0065(50^2) + 0.75(50)
d=0.0065(2500) + 37.5
d=16.25 + 37.5
d=53.75 m (The unit is metres according to the question)

That's right, right? I.. no longer have the power to check for myself.

b) Find v when d is 100 metres
100=0.0065v^2 + 0.75v
I uh, don't seem to remember what to do when there are different powers of a variable being added. Look I know this sounds ridiculous, but I need all the help I can get right now. I'm about to collapse.

I'm gonna try to proceed:
100=v(0.0065v +0.75)
100/(0.0065v + 0.75) = v
Wait what? No, I can't find v in terms of v..

Thanks in advance gyus

edit: My bad. I'm aware this should've been in Ask GBAtemp but there would be no spaces between the lines and it all looks squished and uncomfortable to read, so yeah.
 

FAST6191

Techromancer
Editorial Team
Joined
Nov 21, 2005
Messages
36,798
Trophies
3
XP
28,278
Country
United Kingdom
My usual policy against giving complete answers is in effect.

a) sure.

b) Call it a quadratic equation x=(-b+-sqrt(b^2-4ac))/2a

100=0.0065v^2 + 0.75v

0 =0.0065v^2 + 0.75v - 100
 

Tom Bombadildo

Dick, With Balls
Member
Joined
Jul 11, 2009
Messages
14,568
Trophies
2
Age
29
Location
I forgot
Website
POCKET.LIKEITS
XP
19,122
Country
United States
Damn...FAST beat me to it >.< But yeah, A is INCORRECT I LIED SORRY and for b just subtract 100 and plug it into the quadratic equation.

To expand upon his suggestion, though, here's what the equation should look like:

-.75±SQRT.75^2-(4*.0065*-100)
-----------------------------------------
2*.0065
 

Lucifer666

all the world needs is me
OP
Member
Joined
Apr 22, 2011
Messages
1,626
Trophies
1
Location
The Fourth Dimension
XP
2,160
Country
United Kingdom
Hm, I don't ever remember seeing a formula like this. What math are you taking?

This is just my IGCSE maths course, fairly simple. I'm willing to bet this formula isn't real but just made of for the sake of this question. I guess I can type out the entire question for you.
The stopping distance d m of a car travelling at v km/h is given by d = 0.0065v2 + 0.75v
a) Find the stopping distance of a car travelling at 50 km/h
b) Estimate the speed of a car which takes 100 m to stop

Thanks a lot FAST6191 and Suprgamr232!
But.. hang on, something's not quite right. I know for a fact that the answers PDF provided with my book says the answer is 110 km/h as an estimate. (I don't trust it, it sometimes has a lot of mistakes)

Replacing v with 110 in the equation doesn't give me anything close to 100. Either it's another mistake, or I'm just really crapping out at the moment.
 

Tom Bombadildo

Dick, With Balls
Member
Joined
Jul 11, 2009
Messages
14,568
Trophies
2
Age
29
Location
I forgot
Website
POCKET.LIKEITS
XP
19,122
Country
United States
Hm, I don't ever remember seeing a formula like this. What math are you taking?

This is just my IGCSE maths course, fairly simple. I'm willing to bet this formula isn't real but just made of for the sake of this question. I guess I can type out the entire question for you.
The stopping distance d m of a car travelling at v km/h is given by d = 0.0065v2 + 0.75v
a) Find the stopping distance of a car travelling at 50 km/h
b) Estimate the speed of a car which takes 100 m to stop

Thanks a lot FAST6191 and Suprgamr232!
But.. hang on, something's not quite right. I know for a fact that the answers PDF provided with my book says the answer is 110 km/h as an estimate. (I don't trust it, it sometimes has a lot of mistakes)

Replacing v with 110 in the equation doesn't give me anything close to 100. Either it's another mistake, or I'm just really crapping out at the moment.
B...when I plug in 110 I get 140. So...I think your book is wrong...it's more like...
78.46

WARNING: DON'T LOOK IN THE SPOILERS IF YOU DON'T WANT THE ANSWERS
 

Site & Scene News

Popular threads in this forum

General chit-chat
Help Users
  • No one is chatting at the moment.
  • LeoTCK @ LeoTCK:
    good night
  • BigOnYa @ BigOnYa:
    Nighty night. I messed up, made a margirita but used vodka by accident, taste like shit, but can't bring myself to dump it
  • BigOnYa @ BigOnYa:
    Alright I'm out too, gonna go shoot some 8-ball with the old lady. Good Night all!
  • HiradeGirl @ HiradeGirl:
    G Night
  • NinStar @ NinStar:
    game night
  • wolffangalchemist @ wolffangalchemist:
    Today I learned that raz disposable vapes have 0.96 inch i2c oled screens in them that can be used with various mcu's. I will be getting a bunch from. My coworkers now I j
  • wolffangalchemist @ wolffangalchemist:
    Just need a project to use them in.
  • K3Nv2 @ K3Nv2:
    @BigOnYa watches porn on his vape
  • wolffangalchemist @ wolffangalchemist:
    I made the same joke about a hour ago lol
    +1
  • wolffangalchemist @ wolffangalchemist:
    Seriously co worker said he has like 20 or so of these exact vapes that are empty, I am gonna have a lot of screens and USB c ports.
    +1
  • K3Nv2 @ K3Nv2:
    Use them for meth also
  • SylverReZ @ SylverReZ:
    @K3Nv2, Can it run Crysis?
  • Sicklyboy @ Sicklyboy:
    Holy shit I'm finally below 900 tabs open in Chrome
  • K3Nv2 @ K3Nv2:
    @Sicklyboy, All porn?
  • Sicklyboy @ Sicklyboy:
    >500 of it is youtube videos, so not all porn
  • K3Nv2 @ K3Nv2:
    Good lad
  • wolffangalchemist @ wolffangalchemist:
    i will make a tiny psp and put porn it.
  • NinStar @ NinStar:
    I totally forgot I was a stacked transsexual anthropomorphic bunny on steam
  • BakerMan @ BakerMan:
    ...
  • BakerMan @ BakerMan:
    what the fuck?
  • BakerMan @ BakerMan:
    also, going to bed
  • DinohScene @ DinohScene:
    feckin spambots
  • K3Nv2 @ K3Nv2:
    Wine and dine the spambots before you do that
  • DinohScene @ DinohScene:
    they better pay up
  • K3Nv2 @ K3Nv2:
    They might have grandma's 401k
    K3Nv2 @ K3Nv2: They might have grandma's 401k