ID 783

  K10Which is the smallest?

ID 1010

  K10The typical healthy resting heart rate in adults is 60–80 beats per minute.
If you live 100 years, how many times will your heart beat?

ID 1064

  K10How many whole numbers between 1 and 1000 do not contain the digit 9?

ID 1088

  K10Anna has 9 eggs. She has two empty egg cartons that can hold six eggs each.

How many more eggs does she need to fill the two cartons?

ID 1089

  K10How many eggs are there?

ID 1098

  K10How many black beads are there?

ID 1099

  K10How many line segments are there?

ID 1780

  K10How many 2-digit integers are there in which the sum of the digits is equal to 11?

ID 1947

  K10Which number has the greatest number of divisors?

ID 1952

  K10What is the smallest positive integer that has 12 different positive divisors, including 1 and itself?

ID 2029

  K10How many integers from 1 to 100 can be written as the sum of 3 consecutive positive integers?

ID 2148

  K10What is the largest sum of two integers such that their product is 787?

ID 2231

  K10An hour ago, I notched up 78987 kilometers on my odometer.
The number is palindromic, reading the same backwards as forwards.

How fast was I driving during the last hour if the current number on my odometer is also palindromic?

ID 2265

  K10What is the sum of the digits of all 2-digit numbers?

ID 3144

  K10The speed of sound at sea level is 333 meters / second.

If the sound of an explosion comes 30 seconds later, how far from me was the center of the explosion?

ID 3182

  K10Find the last three digits of the product:

44444 x 99999

ID 3199

  K10How many 2-digit integers are there in which the sum of the digits is equal to 8?

ID 3220

  K10If 144 is divided into three parts proportional to 7, 8 and 9, then the smallest number is

ID 3301

  K10How many digits are in the product of

2101 and 599?

ID 3376

  K10Choose the answer without using a calculator.

Which number is evenly divisible by 8?

ID 3955

  K10Choose some of the two-digit numbers on the right so that they add up to exactly 100.

How many numbers do you use?

Do not use any number more than once.

ID 4071

  K10How many numbers are in the following list of integers:

1, 2, 4, 8, . . . , 2048?

ID 4096

  K10Estimate the number of Metro stations.

ID 4228

  K10How many sets are there of three consecutive positive integers whose product is equal to their sum?

ID 4538

  K10January 1st, 2014 was a Wednesday.

How many Sundays occurred in 2014?

2014 was not a leap year.

ID 4704

  K10What number is largest?

ID 4764

  K10The sum of consecutive integer numbers is 50.

How many numbers are there?

ID 5008

  K10Solve this.

F = (a - x) (b - x) (c - x) . . . (z - x)

ID 5045

  K10If the sum of two numbers is 8 and their difference is 2, what is their product?

ID 5224

  K10Positive integers and zero are whole numbers.

If N is a whole number, any other whole number can be represented by one of the expressions:

ID 5280

  K10Find two numbers so that their sum, product and the result of division are the same.

What is the largest number?

ID 5342

  K10Use three 5's and any math signs to make 19.

How many '+' signs did you use?

ID 5423

  K10The picture "Mental Count" of Russian painter Nikolay Bogdanov-Belsky contains the simple calculation given below.

Which of the following gives the largest result?

Do not use a calculator.

Image source : Wikipedia

ID 5425

  K10Shakuntala Devi was undoubtedly the most brilliant arithmetic mental calculator of all time. In 1977 she mentally calculated the 23rd root of a 201 digit number in a mere 50 seconds. She toured the world showing how she could do calculations faster than they could be entered into and solved by the computers of the day.

The problem for you is much simpler: Evaluate (without using a calculator) the 6th root of the 25 digit number consisting of 1 followed by all zeros.

Author: Leslie Green

ID 5661

  K10If a number is 17 in the hexadecimal (base-16) system, what is it in the decimal system?

ID 5742

  K10What number multiplied by itself is equal to the product of 50 and 98?

ID 5896

  K10The product of any 4 consecutive positive integers is always divisible by

ID 5942

  K10It is demonstrable by direct computer calculation that any even number greater than 5 can be formed as the sum of two odd prime numbers.

Find one of the two primes that sums to 36.

Author: Leslie Green

ID 6106


ID 6178

  K10What is the result when the largest two-digit number is multiplied by the second smallest three-digit number?

ID 6538

  K10Put four operations signs between the numbers 1, 2, 3, 4, and 5 to make the largest possible result.

What will it be?

Change the order of the numbers (but they must still be separated by an operations sign), use all four signs, and don't use brackets.

ID 6551

  K10How many times does the digit 7 appear in the answer to 7654321 x 7 ?

Don't use a calculator.

ID 6975

  K10Cross out 5 digits from the number


so that the remaining number is as large as possible.

What are the first five digits of the result?

ID 7100

  K10Which card represents the highest number in hex?

ID 7193

  K10Do this in your head. No pen, paper, or calculator.

Start with something
multiply it by 3
add 1
multiply the result by 4
subtract 1
The result is 15.

What is the something we started with?

ID 7397

  K10I write a 4-digit number on a sheet of paper, then turn the sheet upside down and the value of the number becomes smaller.

If the ratio of the numbers is about 0.8667, what is the original number?