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Опрос |
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Решение
Every third Alb gives a click. This means no click is awarded until the third Alb is captured. The second click is not awarded until the sixth Alb is captured. Similarly, a tick is not awarded until the fourth Berk is captured.
We are told that the product clicks x ticks = 77. Thus, there are four possibilities: 1 x 77, 7 x 11, 11 x 7, 77 x 1.
| Clicks Awarded | Albs Captured | Ticks Awarded | Berks Captured |
| 1 | 3, 4 or 5 | 77 | 308, 309, 310, or 311 |
| 7 | 21, 22, or 23 | 11 | 44, 45, 46 or 47 |
| 11 | 33, 34, or 35 | 7 | 28, 29, 30 or 31 |
| 77 | 231, 232 or 233 | 1 | 4, 5, 6, or 7 |
Statement (1) tells us that the difference between Albs captured and Berks captured is 7. Looking at the chart, the only way to get a difference of 7 between Albs captured and Berks captured is with 35 Albs and 28 Berks. Therefore, statement (1) is sufficient to answer the question--there must have been 35 Albs captured.
Statement (2) says the number of Albs captured is divisible by 4. Again, looking at the chart, we see that the number of Albs captured must be 4 or 232. Therefore, statement (2) is not sufficient to answer the question--we do not know how many Albs were captured.
The correct answer is A: Statement (1) alone is sufficient, but statement (2) alone is not sufficient.
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What's The Difference?
Question
Set S is the set of all prime integers between 0 and 20. If three numbers are
chosen randomly from set S and each number can be chosen only once, what is the
positive difference between the probability that the product of these three
numbers is a number less than 31 and the probability that the sum of these
three numbers is odd?
(A) 1/336
(B) 1/2
(C) 17/28
(D) 3/4
(E) 301/336
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Вверх 
