Question
A boat takes 7 hours to cover 294 km upstream and 9
hours to cover 486 km downstream. Find the time taken by the boat to cover 720 km upstream and 616 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.Solution
Upstream speed = 294/7 = 42 km/h Downstream speed = 486/9 = 54 km/h Speed of boat in still water = (42 + 54)/2 = 48 km/h  Speed of stream = (54 – 42)/2 = 6 km/h Increased speed of boat in still water = 48 + 4 = 52 km/h Decreased speed of stream = 6 – 2 = 4 km/h Required time taken = 720/(52 – 4) + 616/(52 + 4) = 15 + 11 = 26 hours
The smallest side of a right-angled triangle is 7 cm less than the side of a square of perimeter 76 cm. The second largest side of the right-angled tria...
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The area of an equilateral triangle is 64√3 cm2. Find the radius of the circle that circumscribes the triangle.
