a steel meter rule has correct lenght at 28 degree celcius on the day the temparature is 40 degree celicius,it measures the lenght of a table at 158m .what is the true lenght of the table.alpha=0.000012 raise up to power one per kelvin.

Answer 1

40 - 28 = 12 degrees higher so measured length is longer than true length (The ruler expanded)
error in length / length = 1.2 *10^-5 * 12 deg
error in length = 158 meters (but I think that is a typo)*1.2*10^-5
= 189.6 * 10^-5 meters
= 0.001896 meters
(it is probably centimeters :)
so
158.000000 - .001896

Answer 2

whoops, forgot the 12 degrees, multiply change in length by 12 !!!!