Question
A boat goes 45 km upstream in 6 hours and 60 km
downstream in 4 hours. If the speed of the current is doubled, how much time will the boat take to travel 90 km downstream?Solution
Let the speed of the boat in still water be B km/h and the speed of the stream be S km/h. From the given data: Upstream speed = B - S = 45 km / 6 hours = 7.5 km/h. Downstream speed = B + S = 60 km / 4 hours = 15 km/h. Solving these two equations: B - S = 7.5 and B + S = 15. Adding the two, 2B = 22.5 → B = 11.25 km/h. Substituting B = 11.25 into B + S = 15: S = 3.75 km/h. Now, the speed of the current is doubled, so the new speed of the stream is 2 * 3.75 = 7.5 km/h. The new downstream speed = 11.25 + 7.5 = 18.75 km/h. Time to travel 90 km downstream = 90 / 18.75 ≈ 4.8 hours.
Which can be formed by using the letters of the given word.
GENERALIZATION
Number of times each letter is appearing in the given word is indicated in each alternative. Identify the correct one.
INCIDENCE
Find which one of the given words cannot be formed from the letters of the given word.
‘ STAGGERING ’
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SUPPLEMENTARY
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PROPORTIONAL
