Basic Numeracy/Quantitative Aptitude

Detailed Solution

271. c: 1^st we place the 11#, now there are 10 places between them and 2 on the extreme left and extreme right of them, total places = 10 + 2 = 12
If * is placed at any of these 12 places, no 2 *'s will be together so the number ways will be 12C8 = 12C4 = 495

272. d: The probability will be 1- probability that no blue marbles are selected 1- 3C2 / 10C2 = 14/15
Another method:
1 Blue - 1 Red + 1 Red - 1 blue + Both Blue = 7/10*3/9 + 3/10*7/9 + 7/10*6/9= 14/15.
Since we are not replacing the marbles, order matters and so 1 Blue- 1 Red is not the same as 1 Red- 1 Blue.

273. a: 1^st card that is not blue = 6/8
2^nd card that is not blue = 5/ 7
= 30/56 = 15/ 28
Another method: 1 - P(at least 1 blue card)

274. c: 1 -(probability of same color)
1 -(5C2/10C2 + 3C2/10C2 + 2C2/10C2)
=1 - (10+3+1)/45
= 1 - 14/45 = 31/45
The population of the world is increasing by around 83 million per year. This figure actually represents a decline by almost 50% in the growth rate from its peak of 2.2% in 1963 and further reductions are expected over the coming decades. The 20th century saw the biggest global increase of all time in the population and if the current levels of growth continue the world population will be around 9 billion by the year 2042. The increases are due to increased life expectancy and reduced mortality rates resulting from improvements in healthcare and agricultural productivity. Growth rates vary by region. There are estimates that over 90% of population growth in the future will be in developing countries. Central and Eastern Europe are experiencing a net decrease of population with Japan and some Western European countries expected to follow suit within the next 10 years.

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