Two lorries A and B ferry goods between two towns which are 3120km apart .Lorry A travelled at 5km/h faster than lorry B and lorry B takes 4hours more than lorry A to cover the distance . calculate the speed of lorry B?

4 answers

Speed of lorry B --- x
speed of lorry A ---- x+5 km/h

time for lorry B = 3120/x
time for lorry A = 3120/(x+5)

The slower lorry would take more time, namely 4 hours
so the difference in their times is 4

3120/x - 3120/(x+5) = 4
multiply each term by x(x+5), simplify it, then arrange it
into the standard form of a quadratic.

Use your favourite method to solve, (hint it factors)