Students practice front end estimation with adjustment by rounding numbers before adding them. For estimating an addition problem that involves hundreds, the student rounds each number to the closest hundred and then adds the numbers to find an estimated value.
Front end estimation starts with only using the largest place value of a number. For example, a front end estimation of 413+289+190 is worked as 400+200+100=700. Front end estimation with adjustment rounds each number before adding them, so the same problem is worked as 400+300+200=900. This is a closer estimate of the actual sum 892.
Students first practice front end estimation without adjustment. In separate exercises, they round numbers. Then they combine the two skills to obtain more accurate estimates.