 Aptitude Tests 4 Me

Basic Numeracy/Quantitative Aptitude

Detailed Solution

165. a: Make the equation like this: Let total students be X; So 40% of X + 120 = X;
0.4X+120=X;
120=X-0.4X; 120=0.6X; X=120/0.6; X=1200/6; X=200; So the students 8 year old or younger is 40% of 200; 40/100x200=40x2=80

166. c: Solve the equation like this: Let total students be X;
Students having no brothers or sisters = X/5;
Students having one brother or sister = 40% of (X-X/5) = 40% of 4X/5 = 16/50X;
The students having more than one brother or sister = X – X/5 -16/50X;
Now we have to solve this. (50X-10X-16X)/50 = 24X/50 = 48X/100;
Thus the percentage of such students is 48%

167. The best answer is C.
We have 7!/(4!*3!) = 35 different possibilities for 4 days of rain out of 7 consecutive days (choosing 4 out of seven). Every one of these 35 possibilities has the following probability: every day has the chance of ˝ to rain so we have 4 days of ˝ that it will rain and 3 days of ˝ that it will not rain. We have ˝ to the power of 7 = 1/128 as the probability of every single event. The total is 35 x 1/128 = 35/128.

168. The best answer is D.
For every digit we can choose out of 8 digits (10 total minus 1 and 4). There are four different options:
5. No even digits
6. One even digit.
7. Two even digits.
8. Three even digits.
9. Four even digits.
The probability of choosing an odd (or an even) digit is ˝. One minus the option of no even digits: 1- (1/2)4= 15/16.
You can also sum up all of the other options (2-5).

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