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Pranay SB

· started a discussion

· 1 Months ago

Simpler method: (Question: 277553.0 )

The above would take lot of time to solve:
Here, I am giving you trial and error method which would take 1 minute maximum.
Up.........Down
24...........28...........6hrs -----------------------(1)
30...........21..........13/2 hrs-------------------(2)
Looking at the change in the distances and times I am guessing the times to be 4hr up and 2 hr down. If 4hrs for 24 kms it will be 5hrs for 30 up and 3/2 hrs for 21down.
Now take (1)
*Speed(up)=24/4=6 km/hr
*Speed (down)=28/2=14 km/hr
If you get the same values of speeds, your assumption is correct. If not change the combination (ex 5,1)
Let us check: 30/5=6km/hr and 21/(3/2)=14km/hr.
So our assumption is correct.
Moving forward, speed of the boat in still water is = (Upspeed+downspeed)/2=(6+14)/2=10km/hr
It may look lengthy when u see but, comparatively a simpler method

Question:

A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30 km upstream and 21 km downstream in  612    hours. Find the speed of boat in still water.

Options:
A)

6 km/hr

B)

4 km/hr

C)

8 km/hr

D)

10 km/hr

Solution:

Ans: (d)

  

Knowledge Expert

· commented

· 1 Months ago

Dear Student,
WE have provided general approach to solve the given problem.

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