Estimating in multiplication: round the factors! (4th grade math)
An easy lesson where we estimate products using rounding. The basic rule is to round in such a manner that makes it easy for YOU to multiply mentally. In other words, there are no "hard and fast" rules as to HOW exactly you round when estimating, because it depends on your mental math capabilities.
One good principle to keep in mind is that it is helpful to round one factor UP, the other DOWN, in order to reduce or minimize the error of estimation.
In one example, I do two estimations and take the AVERAGE of those as the final estimation. So that is one more strategy you can use.
We also solve two word problems using estimation (instead of using long division, which could end up being more cumbersome).
This is meant for 4th grade math and on up, as many math curricula never teach strategies for rounding and estimating, or how estimation can be used to solve word problems.
If you cannot see the video above, click here for an alternative video player.
See also
Estimating the final result (in subtraction and in a word problem)
Math Mammoth Grade 4 curriculum