Usually, what you want when you estimate an answer is to know where the decimal place should be. That is, will the final answer be nearer to 1 or to 10? To 100 or to 1000?
The quick and dirty way to find out is to round every number in the problem to the nearest number you can easily handle. That way this calculation:
1028 * (57/4.4) = ?

becomes this one:

(about 1000) * (about 50/ about 5) = (about 1000) * (about 10) = about 10,000

Practice problems:

(217/54) * 322 =

6937 * 45 * 0.4 =

32.477 * (478/309) =

Make up three more practice problems and give their estimated answers: