Question 170196
The first guy can mow a lawn in 6 hours, so he can mow 1/6 of a lawn in 1 hour, the second guy can mow 1/4 of a lawn in 1 hour.  Together they can mow 1/6 + 1/4 of a lawn in 1 hour, or 2/12 + 3/12 = 5/12 of a lawn in 1 hour, so it should take 12/5 hours for both of them to mow the lawn.  12/5 = 2 and 2/5.  1/5 hour is 60/5 = 12 minutes, so 2/5 hour is 24 minutes.  So: 2 hours, 24 minutes.


A 15in TV is measured on the diagonal.  If the width is 12 inches, then use Pythagoras:


{{{L = sqrt(15^2-12^2)}}}


You do the arithmetic



If {{{V = 48T^2}}} gives you vertical displacement in inches (and I think that is right, but you didn't say) simply substitute 30 for V in the formula and solve for T.  Divide both sides by 48 and take the square root.  Again, the arithmetic is up to you.