MathDB

Part 1
p1. Calculate

(4!-5!+2^5 +2^6) \cdot \frac{12!}{7!}+(1-3)(4!-2^4).

p2. The expression

\sqrt{9!+10!+11!}

can be expressed as

a\sqrt{b}

for positive integers

a

and

b

, where

b

is squarefree. Find

a

.
p3. For real numbers

a

and

b

f(x) = ax^{10}-bx^4+6x +10

for all real

x

. Given that

f(42) = 11

, find

f (-42)

.
Part 2
p4. How many positive integers less than or equal to

2023

are divisible by

20

23

, or both?
p5. Larry the ant crawls along the surface of a cylinder with height

48

and base radius

\frac{14}{\pi}

. He starts at point

A

and crawls to point

B

, traveling the shortest distance possible. What is the maximum this distance could be?
p6. For a given positive integer

n

, Ben knows that

\lfloor 20x \rfloor = n

, where

x

is real. With that information, Ben determines that there are

3

distinct possible values for

\lfloor 23x \rfloor

. Find the least possible value of

n

.
Part 3
p7. Let

ABC

be a triangle with area

1

. Points

D

E

, and

F

lie in the interior of

\vartriangle ABC

in such a way that

D

is the midpoint of

AE

E

is the midpoint of

BF

, and

F

is the midpoint of

CD

. Compute the area of

DEF

.
p8. Edwin and Amelia decide to settle an argument by running a race against each other. The starting line is at a given vertex of a regular octahedron and the finish line is at the opposite vertex. Edwin has the ability to run straight through the octahedron, while Amelia must stay on the surface of the octahedron. Given that they tie, what is the ratio of Edwin’s speed to Amelia’s speed?
p9. Jxu is rolling a fair three-sided die with faces labeled

0

1

, and

2

. He keeps going until he rolls a

1

, immediately followed by a

2

. What is the expected number of rolls Jxu makes?
Part 4
p10. For real numbers

x

and

y

x +x y = 10

and

y +x y = 6

. Find the sum of all possible values of

\frac{x}{y}

.
p11. Derek is thinking of an odd two-digit integer

n

. He tells Aidan that

n

is a perfect power and the product of the digits of

n

is also a perfect power. Find the sum of all possible values of

n

.
p12. Let a three-digit positive integer

N = \overline{abc}

(in base

10

) be stretchable with respect to

m

N

is divisible by

m

, and when

N

‘s middle digit is duplicated an arbitrary number of times, it‘s still divisible by

m

. How many three-digit positive integers are stretchable with respect to

11

? (For example,

432

is stretchable with respect to

6

because

433...32

is divisible by

6

for any positive integer number of

3

s.)
Part 5
p13. How many trailing zeroes are in the base-

2023

expansion of

2023!

?
p14. The three-digit positive integer

k = \overline{abc}

(in base

10

, with a nonzero) satisfies

\overline{abc} = c^{2ab-1}

. Find the sum of all possible

k

.
p15. For any positive integer

k

, let

a_k

be defined as the greatest nonnegative real number such that in an infinite grid of unit squares, no circle with radius less than or equal to

a_k

can partially cover at least

k

distinct unit squares. (A circle partially covers a unit square only if their intersection has positive area.) Find the sumof all positive integers

n \le 12

such that

a_n \ne a_{n+1}

.
PS. You should use hide for answers. Rounds 6-9 have been posted [url=https://artofproblemsolving.com/community/c3h3267915p30057005]here. Collected [url=https://artofproblemsolving.com/community/c5h2760506p24143309]here.

Problem Statement