Question

Whats the upper bound for estimate for 354 + 267?

Answer 1

Personally I'd replace 354 with 360 and 267 with 270, and then add 360 and 270, obtaining 630.  Similarly, estimate 63.75 + 3.63 by adding 60 and 3:  63.  There's no single answer for either problem.  For "upper bound," I round the given addends upward; for "lower bound," I found the addends down.