A boat takes 7 hours to cover 259 km upstream and 9 hours to cover 477 km downstream. Find the time taken by the boat to cover 645 km upstream and 660 km downstream if speed of boat in still water is increased by 4 km/h and speed of stream is decreased by 2 km/h.

All desks may be tables. Some stools are not chairs. Some tables may not be chairs.

Statements : Some trains are buses.

  Some buses are trucks.

No truck is a car.

Conclusions:I. Some trains are not trucks.

Statement:

I) No water is air

II) Some air are land

III) All land are floor

IV) Some fire are water

Statements:Some combs are boxes.

All boxes are mirrors.

Conclusions:I. Some boxes are combs. 

II. Some mirrors are combs.

Statement:

Some letters are papers

All papers are objects.

Some objects are subjects.

Conclusion:

Statements:

Only a few Hen are Duck

All Bat are Rat

No Duck is a Bat

Some Rat are Cat

Conclusions:

Statements: All diaries are papers.

Some papers are pens.

No pencil is a paper.

Conclusions:I. No diary is a pencil.

Statements: Some cubs are puppies.

No puppy is a calf.

All kittens are puppies.

Conclusions: I. At least some cubs are calves.

Statement:

Some lights are shadows.

All shadows are wall.

Conclusion:  

I. Some lights are not wall.