User:Ddk001
Contents
- 1 Introduction
- 2 User Counts
- 3 Cool asyptote graphs
- 4 Problems Sharing Contest
- 5 Contributions
- 6 Problems I made
- 7 Answer key
- 8 Solutions
- 8.1 Problem 1
- 8.2 Solution 1
- 8.3 Problem 2
- 8.4 Solution 1
- 8.5 Problem 3
- 8.6 Solution 1(Probably official MAA, lots of proofs)
- 8.7 Solution 2 (Fast, risky, no proofs)
- 8.8 Problem 4
- 8.9 Solution 1
- 8.10 Problem 5
- 8.11 Solution 1 (Euler's Totient Theorem)
- 8.12 Problem 6
- 8.13 Solution 1 (Recursion)
- 8.14 Problem 7
- 8.15 Solution 1
- 8.16 Problem 8
- 8.17 Solution 1
- 8.18 Problem 9
- 8.19 Solution 1(Wordless endless bash)
- 9 See also
Introduction
I am a 5th grader who likes making and doing problems, doing math, and redirecting pages (see Principle of Insufficient Reasons). I like geometry and don't like counting and probability. My number theory skill are also not bad.
User Counts
If this is you first time visiting this page, please change the number below by one. (Add 1, do NOT subtract 1)
Also, I check the pages history so I know if someone edited something.
(Please don't mess with the user count)
Doesn't that look like a number on a pyramid?
Cool asyptote graphs
Asymptote is fun!
Problems Sharing Contest
Here, you can post all the math problem that you have. Everyone will try to come up with a appropriate solution. The person with the first solution will post the next problem. I'll start:
1. There is one and only one perfect square in the form
where and
are prime. Find that perfect square.
(DO NOT LOOK AT MY SOLUTIONS YET)
Contributions
2005 AMC 8 Problems/Problem 21 Solution 2
2022 AMC 12B Problems/Problem 25 Solution 5 (Now it's solution 6)
2023 AMC 12B Problems/Problem 20 Solution 3
2016 AIME I Problems/Problem 10 Solution 3
2017 AIME I Problems/Problem 14 Solution 2
2019 AIME I Problems/Problem 15 Solution 6
2022 AIME II Problems/Problem 3 Solution 3
Restored diagram for 1994 AIME Problems/Problem 7
Principle of Insufficient Reasons
Problems I made
Introductory
1. There is one and only one perfect square in the form
where and
are prime. Find that perfect square.
2. and
are positive integers. If
, find
.
Intermediate
3.The fraction,
where and
are side lengths of a triangle, lies in the interval
, where
and
are rational numbers. Then,
can be expressed as
, where
and
are relatively prime positive integers. Find
.
4. Suppose there is complex values and
that satisfy
Find .
5. Suppose
Find the remainder when is divided by
.
6. Suppose that there is rings, each of different size. All of them are placed on a peg, smallest on the top and biggest on the bottom. There are
other pegs positioned sufficiently apart. A
is made if
(i) ring changed position (i.e., that ring is transferred from one peg to another)
(ii) No rings are on top of smaller rings.
Then, let be the minimum possible number
that can transfer all
rings onto the second peg. Find the remainder when
is divided by
.
7. Suppose is a
-degrees polynomial. The Fundamental Theorem of Algebra tells us that there are
roots, say
. Suppose all integers
ranging from
to
satisfies
. Also, suppose that
for an integer . If
is the minimum possible positive integral value of
.
Find the number of factors of the prime in
.
Olympiad
8. (Much harder) is an isosceles triangle where
. Let the circumcircle of
be
. Then, there is a point
and a point
on circle
such that
and
trisects
and
, and point
lies on minor arc
. Point
is chosen on segment
such that
is one of the altitudes of
. Ray
intersects
at point
(not
) and is extended past
to point
, and
. Point
is also on
and
. Let the perpendicular bisector of
and
intersect at
. Let
be a point such that
is both equal to
(in length) and is perpendicular to
and
is on the same side of
as
. Let
be the reflection of point
over line
. There exist a circle
centered at
and tangent to
at point
.
intersect
at
. Now suppose
intersects
at one distinct point, and
, and
are collinear. If
, then
can be expressed in the form
, where
and
are not divisible by the squares of any prime. Find
.
Someone mind making a diagram for this?
9. Suppose where
and
are relatively prime positive integers. Find
.
I will leave a big gap below this sentence so you won't see the answers accidentally.
Answer key
1. 049
2. 019
3. 092
4. 170
5. 736
6. 895
7. 011
8. 054
9. 077
Solutions
- Note: All the solutions so far have been made by me :)
Problem 1
There is one and only one perfect square in the form
where and
is prime. Find that perfect square.
Solution 1
.
Suppose
.
Then,
, so since ,
so
is less than both
and
and thus we have
and
. Adding them gives
so by Simon's Favorite Factoring Trick,
in some order. Hence,
.
Problem 2
and
are positive integers. If
, find
.
Solution 1
Let and
. Then,
Problem 3
The fraction,
where and
are side lengths of a triangle, lies in the interval
, where
and
are rational numbers. Then,
can be expressed as
, where
and
are relatively prime positive integers. Find
.
Solution 1(Probably official MAA, lots of proofs)
Lemma 1:
Proof: Since the sides of triangles have positive length, . Hence,
, so now we just need to find .
Since by the Trivial Inequality, we have
as desired.
To show that the minimum value is achievable, we see that if ,
, so the minimum is thus achievable.
Thus, .
Lemma 2:
Proof: By the Triangle Inequality, we have
.
Since , we have
.
Add them together gives
Even though unallowed, if , then
, so
.
Hence, , since by taking
and
close
, we can get
to be as close to
as we wish.
Solution 2 (Fast, risky, no proofs)
By the Principle of Insufficient Reason, taking we get either the max or the min. Testing other values yields that we got the max, so
. Another extrema must occur when one of
(WLOG,
) is
. Again, using the logic of solution 1 we see
so
so our answer is
.
Problem 4
Suppose there are complex values and
that satisfy
Find .
Solution 1
To make things easier, instead of saying , we say
.
Now, we have
.
Expanding gives
.
To make things even simpler, let
, so that .
Then, if , Newton's Sums gives
Therefore,
Now, we plug in
.
We substitute to get
.
Note: If you don't know Newton's Sums, you can also use Vieta's Formulas to bash.
Problem 5
Suppose
Find the remainder when is divided by 1000.
Solution 1 (Euler's Totient Theorem)
We first simplify
so
.
where the last step of all 3 congruences hold by the Euler's Totient Theorem. Hence,
Now, you can bash through solving linear congruences, but there is a smarter way. Notice that , and
. Hence,
, so
. With this in mind, we proceed with finding
.
Notice that and that
. Therefore, we obtain the system of congruences :
.
Solving yields , and we're done.
Problem 6
Suppose that there is rings, each of different size. All of them are placed on a peg, smallest on the top and biggest on the bottom. There are
other pegs positioned sufficiently apart. A
is made if
(i) ring changed position (i.e., that ring is transferred from one peg to another)
(ii) No bigger rings are on top of smaller rings.
Then, let be the minimum possible number
that can transfer all
rings onto the second peg. Find the remainder when
is divided by
.
Solution 1 (Recursion)
Let be the minimum possible number
that can transfer
rings onto the second peg. To build the recursion, we consider what is the minimum possible number
that can transfer
rings onto the second peg. If we use only legal
, then
will be smaller on the top, bigger on the bottom. Hence, the largest ring have to be at the bottom of the second peg, or the largest peg will have nowhere to go. In order for the largest ring to be at the bottom, we must first move the top
rings to the third peg using
, then place the largest ring onto the bottom of the second peg using
, and then get all the rings from the third peg on top of the largest ring using another
. This gives a total of
, hence we have
. Obviously,
. We claim that
. This is definitely the case for
. If this is true for
, then
so this is true for . Therefore, by induction,
is true for all
. Now,
. Therefore, we see that
.
But the part is trickier. Notice that by the Euler's Totient Theorem,
so is equivalent to the inverse of
in
, which is equivalent to the inverse of
in
, which, by inspection, is simply
. Hence,
, so by the Chinese Remainder Theorem, .
Problem 7
Suppose is a
-degrees polynomial. The Fundamental Theorem of Algebra tells us that there are
roots, say
. Suppose all integers
ranging from
to
satisfies
. Also, suppose that
for an integer . If
is the minimum possible positive integral value of
.
Find the number of factors of the prime in
.
Solution 1
Since all integers ranging from
to
satisfies
, we have that all integers
ranging from
to
satisfies
, so by the Factor Theorem,
.
since is a
-degrees polynomial, and we let
to be the leading coefficient of
.
Also note that since is the roots of
,
Now, notice that
Similarly, we have
To minimize this, we minimize . The minimum
can get is when
, in which case
, so there is factors of
.
Problem 8
is an isosceles triangle where
. Let the circumcircle of
be
. Then, there is a point
and a point
on circle
such that
and
trisects
and
, and point
lies on minor arc
. Point
is chosen on segment
such that
is one of the altitudes of
. Ray
intersects
at point
(not
) and is extended past
to point
, and
. Point
is also on
and
. Let the perpendicular bisector of
and
intersect at
. Let
be a point such that
is both equal to
(in length) and is perpendicular to
and
is on the same side of
as
. Let
be the reflection of point
over line
. There exist a circle
centered at
and tangent to
at point
.
intersect
at
. Now suppose
intersects
at one distinct point, and
, and
are collinear. If
, then
can be expressed in the form
, where
and
are not divisible by the squares of any prime. Find
.
Someone mind making a diagram for this?
Solution 1
Line is tangent to
with point of tangency point
because
and
is perpendicular to
so this is true by the definition of tangent lines. Both
and
are on
and line
, so
intersects
at both
and
, and since we’re given
intersects
at one distinct point,
and
are not distinct, hence they are the same point.
Now, if the center of tangent circles are connected, the line segment will pass through the point of tangency. In this case, if we connect the center of
tangent circles,
and
(
and
respectively), it is going to pass through the point of tangency, namely,
, which is the same point as
, so
,
, and
are collinear. Hence,
and
are on both lines
and
, so
passes through point
, making
a diameter of
.
Now we state a few claims :
Claim 1: is equilateral.
Proof:
where the last equality holds by the Power of a Point Theorem.
Taking the square root of each side yields .
Since, by the definition of point ,
is on
. Hence,
, so
, and since
is the reflection of point
over line
,
, and since
, by the Pythagorean Theorem we have
Since is the perpendicular bisector of
,
and we have
hence
is equilateral.
With this in mind, we see that
Here, we state another claim :
Claim 2 : is a diameter of
Proof: Since , we have
and the same reasoning with gives
since
.
Now, apply Ptolemy’s Theorem gives
so is a diameter.
From that, we see that , so
. Now,
, so
, so
, and we’re done.
Problem 9
Suppose where
and
are relatively prime positive integers. Find
.
Solution 1(Wordless endless bash)
See also
- My talk page
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