Question
Motor boat covers a certain distance downstream in a
river in 20 hours. It covers the same distance upstream in 30 hours. If the speed of the water is 12 km/hr, then the speed of the boat in still water is:Solution
Let the distance be ‘D’ km According to the question, Downstream speed x + y = d/20 or d = 20 (x+y) .......... (i) Upstream speed x-y = d/30 or d = 30(x-y) ........... (ii) Comparing (i) & (ii) 20(x+y) = 30(x-y) 2(x+y) = 3(x-y) 2x + 2y = 3x - 3y x = 5y Hence, y = Speed of the current = 12 km/hour. Speed of boat, x = 5 × 12 = 60 km/hr
152    142    122   ?     52    2
21, 37, 73, 137, ?, 381
What will come in place of the question mark (?) in the following series?
12, 13, 27, ?, 329, 1646
What will come in place of the question mark (?) in the following series?
325, 292, 262, 229, ?, 166
4, 4, 12, 60, ?, 3780
2807, 1400, 697, 346, 171, 84, 41, ?
254, ?, 1022, 1150, 1214, 1246
143 Â Â Â Â 119Â Â Â Â 107Â Â Â Â 101Â Â Â Â Â 98Â Â Â Â ?
204, 401, 640, ?, 1105, 1406
What will come in place of the question mark (?) in the following series?
60, 94, 184, 464, 1388, ?
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