Erin goes off on a long bike ride, averaging 10 km/h. One hour later her brother Alistair starts chasing after her at 16 km/h. How long will it take Alistair to catch up to Erin?

1 Answer
Jim G.
Jul 17, 2017

#2"hours "#40"mins"

Explanation:

#"using the calculation"#

#• " distance ( D ) "="average speed " xx" time ( t )"#

#"Erin "toD=10t#

#"Alistair "toD=16t-16#

#"since he starts 1 hour later subtract 16 from distance"

#"we require to calculate t for the same distance covered"#

#"solve "16t-16=10t#

#rArr6t=16#

#rArrt=16/6=8/3" hours "=2"hours " 40" minutes"#

#color(blue)"As a check"#

#"for this time they should both have done same distance"#

#"Erin "toD=10xx8/3=80/3" Km"#

#"Alistair "toD=16xx8/3-16=128/3-48/3=80/3" Km"#

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