View Full Version : Please help: r varies directly as s and t; r = 29 for....

P.Gallegos

05-12-2006, 11:09 AM

Find an equation of joint variation. Then solve for the missing value.

r varies directly as s and t. One set of values is r=28, s=7, t=8. Find r when when s=12 and t=9.[/b]

ibueno1

05-12-2006, 11:12 AM

you should try to use this formula r=k*s*t and substitute the numbers into it i hope this helps you :D :D

JOSE JAIME-RODRIGUEZ

05-12-2006, 11:27 AM

The formula r=k*s*t will look like this once you plug in the numbers from your problem:28=k*7*8

Hope this helps get you started!!! 8-)

_____________

JOSE

stacey elias

05-12-2006, 11:31 AM

substitute r,s,t

r=28,s=7,t=8

28=k*7*8

then you multiply both sides by 1/56

1/2 k

r=1/2st

then substitute r=1/2st

r=1/2*12*9

do you know how to finish it now.

stapel

05-12-2006, 02:35 PM

Please review the replies to this almost-identical (http://www.freemathhelp.com/forum/viewtopic.php?t=14529) exercise.

If you get stuck, please reply showing your work. Thank you.

Eliz.

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