Difference between revisions of "2020 AMC 10B Problems"
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==Problem 18== | ==Problem 18== | ||
− | + | An urn contains one red ball and one blue ball. A box of extra red and blue balls lie nearby. George performs the following operation four times: he draws a ball from the urn at random and then takes a ball of the same color from the box and returns those two matching balls to the urn. After the four iterations the urn contains six balls. What is the probability that the urn contains three balls of each color? | |
+ | |||
+ | <math>\textbf{(A) } \frac16 \qquad \textbf{(B) }\frac15 \qquad \textbf{(C) } \frac14 \qquad \textbf{(D) } \frac13 \qquad \textbf{(E) } \frac12</math> | ||
[[2020 AMC 10B Problems/Problem 18|Solution]] | [[2020 AMC 10B Problems/Problem 18|Solution]] |
Revision as of 16:11, 7 February 2020
2020 AMC 10B (Answer Key) Printable versions: • AoPS Resources • PDF | ||
Instructions
| ||
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 |
Contents
- 1 Problem 1
- 2 Problem 2
- 3 Problem 3
- 4 Problem 4
- 5 Problem 5
- 6 Problem 6
- 7 Problem 7
- 8 Problem 8
- 9 Problem 9
- 10 Problem 10
- 11 Problem 11
- 12 Problem 12
- 13 Problem 13
- 14 Problem 14
- 15 Problem 15
- 16 Problem 16
- 17 Problem 17
- 18 Problem 18
- 19 Problem 19
- 20 Problem 20
- 21 Problem 21
- 22 Problem 22
- 23 Problem 23
- 24 Problem 24
- 25 Problem 25
- 26 See also
Problem 1
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 2
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 3
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 4
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 5
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 6
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 7
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 8
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 9
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 10
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 11
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 12
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 13
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 14
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 15
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 16
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 17
These problems will not be available until the 2020 AMC 10B contest is released on Wednesday, February 5, 2020.
Problem 18
An urn contains one red ball and one blue ball. A box of extra red and blue balls lie nearby. George performs the following operation four times: he draws a ball from the urn at random and then takes a ball of the same color from the box and returns those two matching balls to the urn. After the four iterations the urn contains six balls. What is the probability that the urn contains three balls of each color?
Problem 19
In a certain card game, a player is dealt a hand of cards from a deck of
distinct cards. The number of distinct (unordered) hands that can be dealt to the player can be written as
. What is the digit
?
Problem 20
Let be a right rectangular prism (box) with edges lengths
and
, together with its interior. For real
, let
be the set of points in
-dimensional space that lie within a distance
of some point
. The volume of
can be expressed as
, where
and
are positive real numbers. What is
Problem 21
In square , points
and
lie on
and
, respectively, so that
Points
and
lie on
and
, respectively, and points
and
lie on
so that
and
. See the figure below. Triangle
, quadrilateral
, quadrilateral
, and pentagon
each has area
What is
?
Problem 22
What is the remainder when is divided by
?
Problem 23
Square in the coordinate plane has vertices at the points
and
Consider the following four transformations:
a rotation of
counterclockwise around the origin;
a rotation of
clockwise around the origin;
a reflection across the
-axis; and
a reflection across the
-axis.
Each of these transformations maps the squares onto itself, but the positions of the labeled vertices will change. For example, applying and then
would send the vertex
at
to
and would send the vertex
at
to itself. How many sequences of
transformations chosen from
will send all of the labeled vertices back to their original positions? (For example,
is one sequence of
transformations that will send the vertices back to their original positions.)
Problem 24
How many positive integers satisfy
(Recall that
is the greatest integer not exceeding
.)
Problem 25
Let denote the number of ways of writing the positive integer
as a product
where
, the
are integers strictly greater than
, and the order in which the factors are listed matters (that is, two representations that differ only in the order of the factors are counted as distinct). For example, the number
can be written as
,
, and
, so
. What is
?
See also
2020 AMC 10B (Problems • Answer Key • Resources) | ||
Preceded by 2020 AMC 10A Problems |
Followed by 2021 AMC 10A Problems | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AMC 10 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.