You measure the item I think
Not as of 2013. Estimates for the current koala population range between 80,000 and 110,000.
The number of estimates is really up to you. If you're happy with the first one you get, use that company. Three is usually a good minimum. Don't just base it off of price. Check if they offer warranties and check on references.
Close to what it should be
Use estimates and see if the calculation gives an answer that is similar to the exact calculated value.
Search local yellow pages for recomedations. Check better business bureau. Also check with friends and family for recomaditions. Finally get estimates and check for insurance.
Audit
check with the American Medical Association, they have salary estimates for all specialities
Make a preliminary estimate. If you are any good at making estimates and if the final answer is "close" to the estimate then it is reasonable.
Check fuses Check for power to switch Jump switch to operate
check
√ is the close but that is alt 251
One of the latest estimates is about 67.80Â (plus-minus) 0.77 (km/second)/Mpc. Check the Wikipedia article on "Hubble constant" for more details, and other estimates.