At a gathering of
people, there are
people who all know each other and
people who know no one. People who know each other hug, and people who do not know each other shake hands. How many handshakes occur?
245
Line
has equation
and goes through
. Line
has equation
and meets line
at point
. Line
has positive slope, goes through point
, and meets
at point
. The area of
is
. What is the slope of
?
3/4
When
fair standard
-sided dice are thrown, the probability that the sum of the numbers on the top faces is
can be written as
where
is a positive integer. What is
?
84
How many positive integers
satisfy the following condition:
![]()
125
The solution of the equation
can be expressed in the form
. What is
?
8/7
Find the smallest prime that is the fifth term of an increasing arithmetic sequence, all four preceding terms also being prime.
29
Claire adds the degree measures of the interior angles of a convex polygon and arrives at a sum of
. She then discovers that she forgot to include one angle. What is the degree measure of the forgotten angle?
143
Chloe chooses a real number uniformly at random from the interval
. Independently, Laurent chooses a real number uniformly at random from the interval
. What is the probability that Laurent's number is greater than Chloe's number?
3/4
Let
and
be two-digit integers such that
is obtained by reversing the digits of
. The integers
and
satisfy
for some positive integer
. What is
?
154
If log(xy3 ) = 1 and log(x 2y) = 1, what is log(xy)?
3/5
What is the sum of the exponents of the prime factors of the square root of the largest perfect square that divides
?
8
In triangle
the medians
and
to sides
and
, respectively, intersect in point
.
is the midpoint of side
, and
intersects
in
. If the area of triangle
is
, then the area of triangle
is:
24n
A number
is randomly selected from the set
, and a number
is randomly selected from
. What is the probability that
has a units digit of
?
2/5
The integer
is the smallest positive multiple of
such that every digit of
is either
or
. Compute
.
592
Positive real numbers
and
have the property that![]()
and all four terms on the left are positive integers, where
denotes the base-
logarithm. What is
?
10^164
Cozy the Cat and Dash the Dog are going up a staircase with a certain number of steps. However, instead of walking up the steps one at a time, both Cozy and Dash jump. Cozy goes two steps up with each jump (though if necessary, he will just jump the last step). Dash goes five steps up with each jump (though if necessary, he will just jump the last steps if there are fewer than 5 steps left). Suppose that Dash takes 19 fewer jumps than Cozy to reach the top of the staircase. Let
denote the sum of all possible numbers of steps this staircase can have. What is the sum of the digits of
?
13
Triangle
has right angle at
, and contains a point
for which
,
, and
. Find
.
33
James writes down fifteen 1's in a row and randomly writes + or - between each pair of consecutive 1's. One such example is
What is the probability that the value of the expression James wrote down is
?
1001/2^14
Find all primes
such that there exist positive integers
that satisfy
.
2,3,7
What is the value of
21,000
Ten identical crates each of dimensions
. The first crate is placed flat on the floor. Each of the remaining nine crates is placed, in turn, flat on top of the previous crate, and the orientation of each crate is chosen at random. Let
be the probability that the stack of crates is exactly
tall, where
and
are relatively prime positive integers. Find
.
190
A circle of radius
has chords
of length
and
of length 7. When
and
are extended through
and
, respectively, they intersect at
, which is outside of the circle. If
and
, then ![]()
73
An urn contains
green balls and
blue balls. A second urn contains
green balls and
blue balls. A single ball is drawn at random from each urn. The probability that both balls are of the same color is
. Find
.
144
How many positive integers
less than
are there such that the equation
has a solution for
?
412
The value of
that satisfies
can be written as
, where
and
are relatively prime positive integers. Find
.
103