MathDB

[hide=R stands for Ramanujan , P stands for Pascal]they had two problem sets under those two names
Set 1
R1.1 / P1.1 Find

291 + 503 - 91 + 492 - 103 - 392

.
R1.2 Let the operation

a

b

be defined to be

\frac{a-b}{a+b}

. What is

3

-2

?
R1.3. Joe can trade

5

apples for

3

oranges, and trade

6

oranges for

5

bananas. If he has

20

apples, what is the largest number of bananas he can trade for?
R1.4 A cone has a base with radius

3

and a height of

5

. What is its volume? Express your answer in terms of

\pi

.
R1.5 Guang brought dumplings to school for lunch, but by the time his lunch period comes around, he only has two dumplings left! He tries to remember what happened to the dumplings. He first traded

\frac34

of his dumplings for Arman’s samosas, then he gave

3

dumplings to Anish, and lastly he gave David

\frac12

of the dumplings he had left. How many dumplings did Guang bring to school?
Set 2
R2.6 / P1.3 In the recording studio, Kanye has

10

different beats,

9

different manuscripts, and 8 different samples. If he must choose

1

beat,

1

manuscript, and

1

sample for his new song, how many selections can he make?
R2.7 How many lines of symmetry does a regular dodecagon (a polygon with

12

sides) have?
R2.8 Let there be numbers

a, b, c

such that

ab = 3

and

abc = 9

. What is the value of

c

?
R2.9 How many odd composite numbers are there between

1

and

20

?
R2.10 Consider the line given by the equation

3x - 5y = 2

. David is looking at another line of the form ax - 15y = 5, where a is a real number. What is the value of a such that the two lines do not intersect at any point?
Set 3
R3.11 Let

ABCD

be a rectangle such that

AB = 4

and

BC = 3

. What is the length of BD?
R3.12 Daniel is walking at a constant rate on a

100

-meter long moving walkway. The walkway moves at

3

m/s. If it takes Daniel

20

seconds to traverse the walkway, find his walking speed (excluding the speed of the walkway) in m/s.
R3.13 / P1.3 Pratik has a

6

sided die with the numbers

1, 2, 3, 4, 6

, and

12

on the faces. He rolls the die twice and records the two numbers that turn up on top. What is the probability that the product of the two numbers is less than or equal to

12

?
R3.14 / P1.5 Find the two-digit number such that the sum of its digits is twice the product of its digits.
R3.15 If

a^2 + 2a = 120

, what is the value of

2a^2 + 4a + 1

?

PS. You should use hide for answers. R16-30 /P6-10/ P26-30 have been posted [url=https://artofproblemsolving.com/community/c3h2786837p24497019]here, and P11-25 [url=https://artofproblemsolving.com/community/c3h2786880p24497350]here. Collected [url=https://artofproblemsolving.com/community/c5h2760506p24143309]here.

Problem Statement