答案解析请参考文末
Given that??and?
?are both integers between?
?and?
, inclusive;?
?is the number formed by reversing the digits of?
; and?
. How many distinct values of?
?are possible?
Three?vertices?of a?cube?are?,?
, and?
. What is the?surface area?of the cube?
It is given that?, where?
,?
, and?
?are?positive?integers?that form an increasing?geometric sequence?and?
?is the?square?of an integer. Find?
.
Patio blocks that are hexagons??unit on a side are used to outline a garden by placing the blocks edge to edge with?
?on each side. The diagram indicates the path of blocks around the garden when?
.
If?, then the area of the garden enclosed by the path, not including the path itself, is?
?square units, where?
?is a positive integer. Find the remainder when?
?is divided by?
.
Find the sum of all positive integers??where?
?and?
?are non-negative integers, for which?
?is not a divisor of?
.
Find the integer that is closest to?.
It is known that, for all positive integers?,
Find the least positive integer??for which the equation?
?has no integer solutions for?
. (The notation?
?means the greatest integer less than or equal to?
.)
Let??be the set?
?Let?
?be the number of sets of two non-empty disjoint subsets of?
. (Disjoint sets are defined as sets that have no common elements.) Find the remainder obtained when?
?is divided by?
.
While finding the sine of a certain angle, an absent-minded professor failed to notice that his calculator was not in the correct angular mode. He was lucky to get the right answer. The two least positive real values of??for which the sine of?
?degrees is the same as the sine of?
?radians are?
?and?
, where?
,?
,?
, and?
?are positive integers. Find?
.
Two distinct, real, infinite geometric series each have a sum of??and have the same second term. The third term of one of the series is?
, and the second term of both series can be written in the form?
, where?
,?
, and?
?are positive integers and?
?is not divisible by the square of any prime. Find?
.
A basketball player has a constant probability of??of making any given shot, independent of previous shots. Let?
?be the ratio of shots made to shots attempted after?
?shots. The probability that?
?and?
?for all?
?such that?
?is given to be?
?where?
,?
,?
, and?
?are primes, and?
,?
, and?
?are positive integers. Find?
.
In triangle?, point?
?is on?
?with?
?and?
, point?
?is on?
?with?
?and?
,?
, and?
?and?
?intersect at?
. Points?
?and?
?lie on?
?so that?
?is parallel to?
?and?
?is parallel to?
. It is given that the ratio of the area of triangle?
?to the area of triangle?
?is?
, where?
?and?
?are relatively prime positive integers. Find?
.
The perimeter of triangle??is?
, and the angle?
?is a right angle. A circle of radius?
?with center?
?on?
?is drawn so that it is tangent to?
?and?
. Given that?
?where?
?and?
?are relatively prime positive integers, find?
.
Circles??and?
?intersect at two points, one of which is?
, and the product of the radii is?
. The x-axis and the line?
, where?
, are tangent to both circles. It is given that?
?can be written in the form?
, where?
,?
, and?
?are positive integers,?
?is not divisible by the square of any prime, and?
?and?
?are relatively prime. Find?
.
So,?, and hence the surface area is?
.
Since?, the area of the garden is
.
,?
?Remainder?
.
?OR?
Using the first inequality??and going case by case starting with n?
?{0, 1, 2, 3...}:
n=0:??which has no solution for non-negative integers m
n=1:??which is true for m=0 but fails for higher integers?
n=2:??which is true for m=0 but fails for higher integers?
n=3:??which is true for m=0 but fails for higher integers?
n=4:??which is true for m=0 but fails for higher integers?
n=5:??which has no solution for non-negative integers m
There are no more solutions for higher?, as polynomials like?
?grow slower than exponentials like?
.
Using the second inequality??and going case by case starting with m?
?{0, 1, 2, 3...}:
m=0:??which has no solution for non-negative integers n
m=1:??which is true for n=0 but fails for higher integers?
m=2:??which is true for n=0 but fails for higher integers?
m=3:??which has no solution for non-negative integers n
There are no more solutions for higher?, as polynomials like?
?grow slower than exponentials like?
.
Thus there are six numbers corresponding to (1,0), (2,0), (3,0), (4,0), (0,1), and (0,2). Plugging them back into the original expression, these numbers are 2, 4, 8, 16, 3, and 9, respectively. Their sum is?.
The small fractional terms are not enough to bring??lower than?
?so the answer is?
If you didn't know?, here's how you can find it out:
We know?. We can use the process of fractional decomposition to split this into two fractions thus:?
?for some A and B.
Solving for A and B gives??or?
. Since there is no n term on the left hand side,?
?and by inspection?
. Solving yields?
Then we have??and we can continue as before.
Thus, there are no restrictions on??in?
.
It is easy to see that only one of?,?
, and?
?is divisible by?
. So either?
.
Thus,?.
From the?Chinese Remainder Theorem,?. Thus, the smallest positive integer?
?is?
.
Hence the least positive integer??for which the equation?
?has no integer solutions for?
?is?
.
Rewriting the given information and simplifying it a bit, we have
Now note that in order for there to be no integer solutions to??we must have?
?We seek the smallest such?
?A bit of experimentation yields that?
?is the smallest solution, as for?
?it is true that?
?Furthermore,?
?is the smallest such case. (If unsure, we could check if the result holds for?
?and as it turns out, it doesn't.) Therefore, the answer is?
Then?
So,?.
XOXOOXO
The problem may be separated into five cases, since the first shot may be made on attempt 3, 4, 5, 6, or 7. The easiest way to count the problem is to remember that each X may slide to the right, but NOT to the left.
First shot made on attempt 3:
XOXOOXO
XOXOOOX
XOOXOXO
XOOXOOX
XOOOXXO
XOOOXOX
XOOOOXX
Total - 7
First shot made on attempt 4:
Note that all that needs to be done is change each line in the prior case from starting with "XO....." to "OX.....".
Total - 7
First shot made on attempt 5:
OOXXOXO
OOXXOOX
OOXOXXO
OOXOXOX
OOXOOXX
Total - 5
First shot made on attempt 6:
OOOXXXO
OOOXXOX
OOOXOXX
Total - 3
First shot made on attempt 7:
OOOOXXX
Total - 1
The total number of ways the player may satisfy the requirements is?.
The chance of hitting any individual combination (say, for example, OOOOOOXXXX) is?
Thus, the chance of hitting any of these 23 combinations is?
Thus, the final answer is?
WLOG, let?.
Then:
.
.
.
.
Thus,?. Therefore,?
, and?
.
Now use similarity, draw perpendicular from??to?
, name the new point?
. Triangle?
?is similar to triangle?
, by AA Similarity. Equating the legs, we get:
Solving for?, it yields?
.
The??cancels, yielding a quadratic. Solving yields?
. Add?
?to find?
, yielding?
?or?
.
It follows that??and?
?are the roots of the quadratic
It follows from Vieta's Formulas that the product of the roots of this quadratic is?, but we were also given that the product of the radii was 68. Therefore?
, or?
. Note that the half-angle formula for tangents is
Therefore
Solving for??gives that?
. It then follows that?
.
It then follows that?. Therefore?
,?
, and?
. The desired answer is then?
.
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