Let the speed of the bus be xkm∕hr Speed of car =88km∕hr ⇒ Relative speed =(88−x)km∕hr Total distance covered in 40 seconds =120+80=200m According to the question (88−x)×40×5∕18=200 Multiplying by 5∕18 to convert the units into m∕sec. (88−x)×5∕18=200∕40 ⇒88−x=5×18∕5 ⇒88−x=18 ⇒x=88−18 ⇒x=70km∕hr ∴ Speed of bus is 70 km/hr