Guys I need to find r from this formula 0.0680 = TTr^{2 x .040 x 7800 x (r2 /2)}

Guys I need to find r from this formula 0.0680 = TTr^{2 x .040 x 7800 x (r2 /2)}
i would do the calculations available,.40 times 7800...this will reduce the terms....
I have taken a pic of the problem as the answer did not work the Answer should be around 243. see attachement
The answer provided by strange is the correct solution for 'r' given the equation you provided so you now have three possibilities,
1.) The answer is not supposed to be something like 243.
2.) The wrong values were substituted into the equation. (i refer to 'I', 'p' and 't')
3.) The wrong equation is being used to solve the problem.
If the equation used was provided to you in the question then you can rule 3 out. If the values substituted were explicitly given then 2 can be ruled out as well.
It is a very odd looking expression (why r^{2} twice?) so I suspect it may have been written down incorrectly...
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