The first question what is the answer

(a) 21 km

(b) 15 mins

(c) 84 km/h

Explanation:

Distance covered is given by subtracting the initial reading from final reading hence

Distance is 53840-53819=21 km

Time taken is given by subtracting the initial time from final time hence

Time is 8:30-8:15=15 mins

Speed is defined as rate of change of distance per unit time. The first part we found distance while second part we found time. Converting the time given into hours we shall have 15/60=0.25 hours. Therefore,

Speed is 21/0.25= 84 km/h

21km

15min

1.4km/min

Explanation:

Distance of car at 8:15am  = 53819km

Distance of car at 8:30am = 53840km

Unknown:

Distance covered by car = ?

Time taken  = ?

Speed  = ?

Solution:

This is a motion problem and it is easy to solve;

  Distance is the length of path covered by a moving body

   Time is the duration of the motion

  Speed is the rate of change of distance with time:

                Speed  =

Distance covered  = 53840 - 53819  = 21km

Time taken  = 8:30  -  8:15  = 15minutes

Speed  =  = 1.4km/min

wire in brush may conduct electricity from cell to drill and vice versa electrc shock possible