Estimate a Sum by Rounding - Arithmetic Step by Step

Estimate 384 + 257 by rounding each addend to the nearest ten first: 380 + 260 = 640, which is close to the exact answer of 641.

Example

estimate-384-257.math

   384
+  257
------

step: round 384: ones=4 -> round down -> 380
step: round 257: ones=7 -> round up -> 260
step: estimate: 380 + 260 = 640
step: exact: 384 + 257 = 641

estimation Round each number to the nearest ten, then add the rounded values. The result is an estimate — close to the exact answer but easier to compute mentally. Rounding before adding reduces the chance of arithmetic errors.