We drive at a speed of 20 km/h for 3 hours. Then we drive 4 hours at 30 km/h. Calculate our average speed.

First speed = 20km/h

Time = 3 hours

Distance = 3×20

= 60 km

Second speed = 30km/h

Time = 4 hours

Distance = 4×30

= 120 km

Total distance = 60+120 = 180km

Total time = 3+4 = 7 hours

Average speed = 180/7

= 25.71 km/h

Hope this will help...

Nps pollution is caused by rainfall or snowmelt moving over and through the ground. nonpoint source pollution can include: excess fertilizers, herbicides and insecticides from agricultural lands and residential areas. oil, grease and toxic chemicals from urban runoff and energy production

Electoral current force mechanical advantage if the wheel and axle is 2 n and the output force is 20 n