You drive to the city at an average speed of 40 km/h and return at an average speed of 60 km/h. find your average speed for the entire trip? explain why the answer is not 50 km/h.

Well, let's see:

If you live 'D' kilometers from the city, and you go and return by the same route, then

-- The time it takes you to reach the city, at 40 km/h, is  D/40  hours.

-- The time it takes you to return, at 60 km/h, is    D/60.

-- The total distance you cover is  2D, and the total driving time is

                        (D/40) + (D/60)

                   =  (3D/120)  +  (2D/120)

                   =        5D/120  =  D/24

-- Your average speed for the entire trip is

                         (distance covered)  /  (time to cover the distance)

                   =            ( 2D )   /   ( D/24 )

                   =              48 km/hr.  

answer and explanation;

composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock while texture refers to the size and arrangement of the minerals or grains that make up a rock. both composition and texture can be used to classify rocks, such as igneous rocks. texture describes how the rock became solid or crystallized from liquid, melted rock. composition of a rock describes the minerals that make up a particular rock.