Question

While driving on the highway, Fiona averages 60 miles per hour. In the city, she averages 30 miles per hour. On a trip to her grandmother's house, Fiona drives 312 hours on the highway and 112 in the city. What is Fiona's average speed for the entire trip to her grandmother's house?

Answer 1

$((312 \div (312 + 112)) \times 60mph) + \\ ( (112 \div (312 + 112)) \times 30mph) \\ = 52.1mph(3 \: s.f.)$