Sun	Mon	Tue	Wed	Thu	Fri	Sat
23	24	25	26	27	28	1
2	3	4	5	6	7	8
9	10	11	12	13	14	15
16	17	18	19	20	21	22
23	24	25	26	27	28	29
30	31	1	2	3	4	5

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Multiple Choice Questions

A boat can cover 25 km upstream and 42 km downstream together in 7 hours Also it can cover 30 km ups...........

Quantitative Aptitude (CCS) Boats and Streams

A boat can cover 25 km upstream and 42 km downstream together in 7 hours. Also it can cover 30 km upstream and 63 km downstream together in 9 hours. What is the speed of the boat in still water?

13 km/hr

8 km/hr

7 km/hr

11 km/hr

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Explanation:

Solution:
Upstream speed in both cases is 25 and 30 resp. Ratio is 25 : 30 = 5 : 6. So let times in both cases be 5x and 6x
Downstream speed in both cases is 42 and 63 resp. Ratio is 42 : 63 = 2 : 3. So let times in both cases be 2y and 3y
So 5x + 2y = 7
and 6x + 3y = 9
Solve both, x = 1, y = 1
So upstream speed is = 25/5x = 5 km/hr
And downstream = 42/2y = 21 km/hr
So speed of boat is 1/2 * (5+21) = 13

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