Is calculation the only way?

[mwilliams82]

The more I study the gmat the more obsessed I've become with finding out how to find answers w/o calculation. I know how to calculate such problems as the following but have realized calculation is often the number one culprit that derails my timing and causes careless errors. SO, can the following problem be solved by ball-parking or abstract logic?

If T= 5/9(K-32), and if T= 290, then K=

(a) 17938/9
(b) 322
(c) 490
(d) 554
(e) 2898/5

Thanks in advance!

[sunny.jain]

Well, you can choose to do half calculation:

T = 5*(k-32)/9

290*9/5 = K - 32

58*9 + 32 = K

just calculate the unit digit:
8*9 + 2 = 4, so D is the answer.

[anoo.anand]

( 290* 9 / 5 ) + 32 = k

=> k = ( 290 * 10 /5 ) + 32

= ( 290 * 10 * 2 / (5*2) ) + 32

= double of 290 + 32

= approx 600 but in 550 range... ;) ...so D

[RonPurewal]

The more I study the gmat the more obsessed I've become with finding out how to find answers w/o calculation. I know how to calculate such problems as the following but have realized calculation is often the number one culprit that derails my timing and causes careless errors. SO, can the following problem be solved by ball-parking or abstract logic?

If T= 5/9(K-32), and if T= 290, then K=

(a) 17938/9
(b) 322
(c) 490
(d) 554
(e) 2898/5

Thanks in advance!

this was a GMATPREP problem? really?

anyway, mwilliams, the best thing for you to do is check out grade-school arithmetic and pre-algebra textbooks from the library, and PRACTICE.

i am not kidding.
you can't expect to run the other way every time you see arithmetic on the test!

not to mention that practicing your arithmetic is WAY easier than trying to develop a whole new theory on how to circumvent doing arithmetic.