The kangaroo will sprint 50m in 2 seconds as

100 meters in 4 seconds, so-

it will be 50 meters in 2 seconds. (Half of 4 is 2, and half of 100 is 50, so it will be 50 meters in 2 seconds.)

The Brainliest Answer!
We know that                             SPEED = DISTANCE/TIME TAKE
distance travelled by kangaroo      = 100m and 50m
time taken                                   = 4sec and 2sec
as we know the formula of speed
   Speed  =  100/4sec
              =   25m/sec
speed of kangaroo in the first case was 25m/sec
In the same way for the second case
   Speed  =  50/2sec
              =  25m/sec
therefore average speed of kangaroo is 25m/sec 
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