ID 861

  K11The speed of light is 3 x 105 kilometers/second.

If the sun is 1.5 x 108 kilometers from Earth, how many seconds does it take light to reach the Earth?

ID 1100

  K11How many red circles are there?

ID 1101

  K11How many people are there?

ID 1103

  K11Which gives the largest answer?

ID 1104

  K11How many digits are there?

ID 1105

  K11How many triangles are there?

ID 1107

  K11How many small square cells are there in the diagram on the right?

ID 1148

  K11Which of these shows the largest number of arrows?

ID 1165

  K11Which gives the smallest number?

ID 1183

  K11What is the difference between the best and the worst results?

ID 1244

  K11The North American emergency telephone number is 911.

How many three-digit integers are exactly 911 more than a two-digit integer?

ID 1388

  K11Choose the answer without using a calculator.

Which number is evenly divisible by 8?

ID 1408

  K11How many sets of at least two consecutive positive integers have a sum of 15?

ID 1820

  K11What is the sum of all the digits (not numbers) in the sequence 1, 2, 3, 4, . . . 98, 99?

ID 1894

  K11How many three-digit numbers which are multiples of 7 end with the digit 4?

ID 2185

  K11The date July 31, 1370 in MM/DD/YYYY format is a palindrome that may be read the same way in either direction (the same forwards as backwards).

How many such dates are there from June 1, 1352 to June 1, 2012?

ID 2212

  K11We use the decimal number system with base 10.
The binary numeral system (base 2) is widely used for digital computations.

In a number system, 17 is a prime number.
A prime number is a positive integer that has no positive divisors other than 1 and itself.

What is the base of the number system?

ID 2224

  K11How many two-digit numbers have exactly five divisors including 1 and themselves?

ID 2274

  K11Make 33 by using three 3s and any math operators.
How many times do you use the plus sign (+) in the expression?

ID 2277

  K11The sum of two prime numbers is equal to 888.
There are several options. We look for two numbers with maximum product.

What is one of the numbers?

ID 3176

  K11The last digit of the number 9100 is

ID 3191

  K11The typical healthy resting heart rate in adults is 60–80 beats per minute.
If you live 80 years, how many times will your heart beat?

ID 3536

  K11Pairs of primes separated by a single number are called prime pairs. Examples are 809 and 811.

The number between a 3-digit prime pair is always divisible by:

ID 3539

  K11Find the last 3 digits of the sum of

1 + 11 + 111 + . . . + 111 . . . 111,

where the last number has 99 ones.

ID 3591

  K11A number is palindromic, if it is the same backwards as forwards.

Of the largest palindrome made from the product of two two-digit numbers, find one of the numbers.

ID 3686

  K11If you sum all the numbers between 1 and 11111, what number is the result?

By the way, 1 is odd.

ID 3699

  K11Which is not correct?

Remember that
3! = 1 x 2 x 3

ID 3946

  K11You can throw an unlimited number of darts at the dartboard.
Some total scores are impossible to obtain, such as all the numbers less than 5 as well as 6, 8, and 9.

What is the highest whole number score that is impossible to obtain?

The Dart Problem by Bill Graham in Games Magazine (August 2003)

ID 3952

  K11How many sets of three consecutive integers whose product is equal to their sum are there?

ID 4045

  K11If the sum of three distinct positive integers is 33, what is the maximum possible product of the numbers?

ID 4340

  K11The product of two integers is 1000.
Neither of the numbers contains a zero.

Find the sum of the integers.

ID 4684

  K11What is a mystery number if you add it to 1, then multiply by 2, then add 3, then multiply by 4, you get 5?

ID 4760

  K11The product of 99 integers is 99.

What is the largest possible value the sum of the numbers can have?

ID 4932

  K11What is the smallest number greater than 2000 that is evenly divisible by all of 2, 3, 4, 5 and 6?

ID 5000

  K11How many digits are in the number 2015?

ID 5030

  K11What is the smallest 7-digit prime number?

A prime number is a natural number that has no positive divisors other than 1 and itself.

ID 5169

  K11Leslie Green asks:

Find the ratio A/B where A is the number of elements in the set of all positive integers
and B is the number of elements in the set of all even positive integers.

ID 5190

  K11As n goes to infinity, what is the limit of n / (n-1)?

ID 5206

  K11The product of real positive numbers a, b, c, and d is equal to 1.

What is the minimum value of their sum?

ID 5267

  K11The sum of the digits of a four-digit number is 15.
All the digits are different and they are in decreasing order.
Each digit is a power of 2.

What is the sum of the first two digits?

ID 5322

  K11Find the sum of the digits of the first 100 positive integers:

1 + 2 + 3 + . . .

ID 5576

  K11{ Positive Odds } = { 1, 3, 5, 7, 9, 11, … }

How many positive integers less than 100 have only odd digits?

ID 5662

  K11If a number is 10111 in the binary (base-2) system, what is it in the decimal system?

ID 5665

  K11What is the units digit of the product of all positive two-digit integers which are evenly divisible by 11?

ID 5965

  K1172 - 52 = 40

Which digit should be moved to make the above equation correct?

ID 6075

  K11The sum of the digits of a seven-digit even integer is 7.

What is the product of these digits?

ID 6253

  K11Binary 11 means 1x21 + 1x20 = one two and one one.
101 is 1x22 + 0x21 + 1x20 = 4 + 0 + 1 = 5 (decimal number system).

When the number 2017 is written in the binary system, how many digits will it have?

ID 6272

  K11Given that

7 + 1 = 10
5 + 3 = 10
10 + 10 = 20

What is: 17 + 1 = ?

ID 6592

  K11The square root of 121 is 11.

What is the square root of the number 12345678987654321?

ID 6727

  K11This sequence of numbers repeats so they could be written in a circle (after deleting the 1 and 6 at the end, since they just show the repeat point).
There is a definite mathematical rule to go from one number to the next.

1,   6,   4,   3,   0,   5,   3,   1,   6, . . .

Sadly one (and only one) of the numbers has been mis-typed, but which one?

Author: Leslie Green

ID 6955

  K11What is the largest possible remainder that can be obtained when a two-digit number is divided by the sum of its digits?

ID 7071

  K11Which row contains both the square of a positive integer and the cube of a different positive integer?

This is a typical SAT question.