good max/min question (2 Viewers)

[barbernator]

here's a good maxima and minima question to test your ability.

the cost of running a car at an average speed of v km/h is given by

c=150 + (v^2/80) cents per hour

Find the average speed, to the nearest km/h, at which the cost of a 500km trip is a minimum.

 

[deswa1]

Is v 109 km/h. I rushed through it so I wouldn't be surprised if its wrong... Its a good question though.

 

[qwerty44]

Is v 109 km/h. I rushed through it so I wouldn't be surprised if its wrong... Its a good question though.

I got 110 km/h for V.

 

[deswa1]

I got 110 km/h for V.

Probably the same answer as mine. I didn't look at the calc properly, just the digits in front of the decimal place so you'll be right.

 

[barbernator]

yeh thats it

 

[qwerty44]

Probably the same answer as mine. I didn't look at the calc properly, just the digits in front of the decimal place so you'll be right.

Yeh the answer was 109.5445115, just a rounding error. It was a good question though.

 

[barbernator]

Is v 109 km/h. I rushed through it so I wouldn't be surprised if its wrong... Its a good question though.

1/2 lol. no half marks

 

[qwerty44]

btw barb:

http://community.boredofstudies.org/showthread.php?t=181717

 

[barbernator]

btw barb:

http://community.boredofstudies.org/showthread.php?t=181717

hahahaah so did u cheat then? our school uses margaret grove, it's a horrible textbook, but that is a good one from it

 

[qwerty44]

Haha I knew someone would think that, but no I didn't. I am doing HSC 2U and had a half yearly testing max and min, so I have done this questions before. It is also similar to the 1992 HSC paper Q10 which I have also done.

 

[deswa1]

This is similar to a hard 3U question from the 90's or early 2000's. I'll track it down and post it so you can have a go.

 

[barbernator]

This is similar to a hard 3U question from the 90's or early 2000's. I'll track it down and post it so you can have a go.

i think i know the one u are talking about, with a plane and s=d/t.

 

[deswa1]

i think i know the one u are talking about, with a plane and s=d/t.

Yep. That's the question. Here it is (if you guys can get part ii, then you should be set for maxima and minima):

Sorry for not making the picture appear (I still can't do that haha)

 

[barbernator]

Sorry for not making the picture appear (I still can't do that haha)

yeh same for me haha, nightweaver tried to teach me but i failed

 

[nightweaver066]

lol guys.

Follow this template:

 

[barbernator]

 

[nightweaver066]

Make sure the link ends in .png, .jpg, .jpeg or .bmp etc.

 

[barbernator]

 

[barbernator]

y u have no dp weaver?

 

[nightweaver066]

y u have no dp weaver?

I haven't bothered to put one up haha.

I thought you had one?