Direct Variation Question (1 Viewer)

[aaronzimmermann]

Hey, this is my first forum post!

Anyway, I have a question, for the multiple choice question #19 on the 2008 paper, I keep getting A but apparently the correct answer is B.

Here's a link to the paper:

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2008exams/pdf_doc/2008HSC-general-mathematics.pdf

Here's my working out:

35 = k / (√2000)

k = 35 * (√2000)

k = 1565.2

============================

h = 1565.2 / (√10000)

h = 15.652

Thanks in advanced.

 

[emma211]

The question says it is DIRECTLY proportional so your working with this equation:
y=k x the square root of t

(this will be my square root sign: *)

To Find the constant:
y = k x *t

35= k x *2000

35= 44.72135955k

35/44.72135955=k

0.7826237921=k

To find the height of the mound:

h=0.7826237921 x *10 000
= 78.26
= B

you used the indirect formula

hope that helps.

 

[aaronzimmermann]

Oops ahaha yeah just figured out that I was using the inverse variation method, my bad. Hopefully somebody can learn from this mistake.

Thanks emma, good luck tomorrow! I'm so glad english is over I hate it.

 

[emma211]

no probs

yeah good luck to you aswell...hopefully it'll be alright.

yer so happy english is finished..biggest relief