Explain how you can estimate to tell whether 433_147=286 is reasonable

Initial Problem:

443-147=286

Estimated Problem:

400-100=300

286 ^ (rounded up) = 300

therefore answer is reasonable since

300=300

Steps:

Round to the nearest hundred (in most cases)

443 (round down) = 400

147 (round down) = 100

You round down those two numbers since second digit is less than 5

400-100 = 300

286 round up, since second digit is more than 5

Therefore 300=300. It is reasonable