a) 4.5 hours
b) 4 hours
c) 5.4 hours
d) 6 hours
Answer: b
Explanation: Let the speed of the stream be x kmph and both the boats meet after t hour.
According to the question,
(12 + x) × t + (15 – x) × t = 108
12t + 15t = 108
27t = 108
∴ t = $$\frac{{108}}{{27}}$$ = 4 hours
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