UGC NET Questions (Paper – 1)

A is correct because with downstream speed (b + s) and upstream speed (b − s), their average is b, the still-water speed. B is correct as the stream’s speed is half the difference of downstream and upstream speeds. D is true because if stream speed is zero, upstream and downstream speeds coincide, and E applies the standard time = distance ÷ speed relation used in these problems. C is false because upstream travel is slower and hence takes more time than downstream for the same distance. Therefore, A, B, D and E only are correct.

Option A:
Option A lists A, B and D but omits E, failing to mention the basic time formula that underlies most calculations in these problems. Because it does not include all true statements, it is incomplete.

Option B:
Option B is correct as it groups all true statements and excludes C, which reverses the comparison of upstream and downstream times. It reflects how relative speed, still-water speed and stream speed are handled in aptitude questions.

Option C:
Option C wrongly includes C, which claims upstream time is always less, and omits A, failing to describe the average-speed relationship. Including C makes this option logically incorrect.

Option D:
Option D includes C as well, and therefore it too inherits the error that contradicts basic time–speed relationships, despite including some correct statements. Hence it cannot be the right answer.

Statements A, B, C and D correctly describe standard boats and streams situations. A and B give the definitions of downstream and upstream speeds. C is true because if u − v = u + v, then v must be zero. D is correct since when the stream speed is non-zero, going against the current reduces effective speed and increases travel time for the same distance. E is false because if the stream is faster than the boat in still water, the boat cannot progress upstream relative to the ground. Therefore, A, B, C and D only are correct.

Option A:
Option A is incomplete as it omits C and D, both of which provide important consequences of the definitions, one algebraic and one about time comparisons in exam problems.

Option B:
Option B is also incomplete since it excludes D, missing the key implication that upstream travel takes longer when there is a current.

Option C:
Option C is wrong because it drops A and includes only B, C and D, leaving out the basic downstream speed definition that underlies the others.

Option D:
Option D is correct because it includes all the true statements and properly excludes E, which incorrectly permits upstream motion even when the current is stronger than the boat’s still-water speed.