Question

A plane travels at 212 miles per hour

Answer 1

See below

Explanation:

212 mile/hr to 1 SD = 200 mile/hr

4000 sec/ hr / 200 mile/ hr = 20 sec / mile

OVER or UNDER ?

actual :

3600 / 212 = 16.98 sec / mile

so 20 sec / mile is an OVER ESTIMATE