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kym02
A bird flies 42 mph across a lake. If the lake is 3 miles across, find the time the bird took in a) seconds b) minutes and c) hours.
time taken by the bird is \[t=\frac{ D }{ v } \]
convert 42 mph in mps for that you can use this relation 42 miles --- 1 hour ---60 minutes ---60*60 seconds 42 miles --- 3600 seconds in 3600 seconds -- 42 miles therefore in 1 second it will be \[\frac{ 42 }{ 3600 } miles= 0.011 miles\] therefore your mps is = 0.011 miles per second
now time t is \[t= \frac{ 3 }{ 0.011 }=272 s\]
for minutes just divide 272 by 60 , because in each minute there are 60 seconds so 272/60= 4.533 minutes and in hours just divide 4.533 by 60 again so it will be 0.0755 hours , hope that helps you :D