Answer: 12 red balls must be added
Step-by-step explanation:
Starting out with 15 balls, 6 red implies 9 blue. If blue remains 9, then we expect red to be 18 for a probability at 2/3. 18-6 = 12
Answer:
B
Step-by-step explanation:
In the case of this distance, trying to imagine 5 x 10^6 is obviously way too ridiculous
Answer:
Speed of boat in still water is 6km/h
Speed of current is 4km/h
Step-by-step explanation:
We know speed = distance / time
Let the speed of boat in still water be x
Let the speed of current be y
Hence the speed of boat, down stream = 
Distance downstream = 20km
Time taken = 2 hours
We have

......(1)
Speed of boat upstream = 
Distance upstream = 4
Time taken = 2
We have

...(2)
Adding (1) & (2)


Substituting in (1) we get
