Question
A motor-cycle covers 90 km with a speed of 40 km/hr.
find the speed of the motor-cycle for the next 90 km journey so that the average speed of the whole journey will be 60 km/hr.Solution
Average speed of whole journey = 60 km/hr Using the formula, average speed = 2xy/(x + y)  x = speed of first 90 km = 40 km/hr 60 = 2 x (40 x y)/(40 + y) = 120 km/hr
7, 26, 238, 962, 8522, 34078
12                          13                         30                     �...
14Â Â Â 42Â Â Â Â 105Â Â Â Â 210Â Â Â Â Â 315Â Â Â ?
8      24       48      144      ?     864
...Find sum of first n terms: 2 + 6 + 12 + 20 + 30 + …
6Â Â Â Â Â Â Â Â Â Â Â Â Â Â 3Â Â Â Â Â Â Â Â Â Â Â Â Â Â 24Â Â Â Â Â Â Â Â Â Â Â 218Â Â Â Â Â Â Â Â Â 3486Â Â Â Â Â Â Â 43575
10      �...
Which of the following is true about the relation between the wrong numbers in the following series?
I: 10, 18, 29, 40, 54, 70
II: 15, 24,...
Study the given pattern carefully and select the number that can replace the question mark (?) in it.
4 7 6
15 ? 21
44 68 60
100Â Â Â Â 221Â Â Â Â 77Â Â Â Â 245Â Â Â Â 50Â Â Â 275
22   39    58    81   ?      141
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