dave13 wrote:
Bunuel wrote:
HKD1710 wrote:
In a given river, the current is 6 mph. A certain riverboat can travel 18 mph in still water. How far upstream (against the current) can the boat travel if a round trip is to take 10 hours?
A) 24
B) 48
C) 60
D) 80
E) 96
The upstream speed = the boat speed - the current speed = 18 - 6 = 12 mph;
The downstream speed = the boat speed + the current speed = 18 + 6 = 24 mph.Since the downstream speed of the boat is twice that of the upstream speed, then travelling downstream would take the boat half the time it would take it to travel upstream: t/2 + t = 10 hours, which gives t = 20/3 hours.
In 20/3 hours, the boat will travel upstream (time)(rate) = 20/3*12 = 80 miles.
Answer: D.
dave13 wrote:
bunuel is it relative speed concept ?
Hi
dave13, bunuel is on South African safari vacation now
, so i will respond on his behalf
since i am trained in MATH
OKAY so i did some online research AND YES ! this a a relative speed concept you must KNOW AND MORE IMPORTANTLY - REMEMBER IT !
Relative speed is defined as the speed of a moving object with respect to another. When two objects are
moving in the same direction, relative speed is
calculated as their difference.EXAMPLE: The upstream speed = the boat speed - the current speed = 18 - 6 = 12 mph
When the two objects are
moving in opposite directions, relative speed is computed by
adding the two speeds.
EXAMPLE: The downstream speed = the boat speed + the current speed = 18 + 6 = 24 mph
for more information please refer to the link below In other words just click on it MAN!!!
https://www.toppr.com/guides/quantitati ... /upstream/