SOLUTION: half of me is greater than 20, one of my digits is double the other ,one of my digits is a perfect square. what number am i ? am i a prime or composite ?

Question 364536: half of me is greater than 20, one of my digits is double the other ,one of my digits is a perfect square. what number am i ? am i a prime or composite ?
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

If one of the digits is a perfect square, then that digit has to be 1, 4, or 9 because these are the only perfect square single digits.

If the perfect square digit is 1, then the 'double the other digit' has to be 2 (you can't have a digit of 1/2). The largest number you can make from 2 and 1 is 21, but half of 21 is not greater than 20. Therefore, exclude 1.

If the perfect square digit is 9, then there is no 'double the other digit' because half of 9 is 4.5 which can't be a digit, and double 9 is 18 which is two digits and therefore can't be a digit. Exclude 9.

If the perfect square digit is 4, then half of 4 is 2. You could have 24, but half of 24 is 12 which is not greater than 20. You could have 42 which fits all criteria. But half of 8 is 4, so therefore you could have either 48 or 84 that also fit all three criteria.

Hence there are three answers: 42, 48, and 84. All three are obviously composite because they are even numbers greater than 2.

John

My calculator said it, I believe it, that settles it

The Out Campaign: Scarlet Letter of Atheism

RELATED QUESTIONS
I AM A WHOLE NUMBER HALF OF ME IS GREATER THAN 20, ONE OF MY DIGITS IS DOUBLE THE OTHER... (answered by ankor@dixie-net.com)

i am a number. i have four digits. My thounsads digit is half my tens digit. my one digit (answered by josmiceli)

each of my five digits is one more than the digit to its left.the sum of my digits is... (answered by DrBeeee,MathTherapy)

I am a square number less than 100. One of my digits is 8 less than twice the other. Who... (answered by solver91311)

I am a perfect square. The sum of my digits is 10, I'm less than 50, whats my... (answered by Alan3354)

I am a 4 digit number greater than 9,000. My hundreds digit is twice my ones digit. (answered by richard1234)

I am a perfect square. The sum of my digits is 10, I'm less than 100, who am... (answered by ikleyn)

i am a number that is greater than 95. the sum of my digits is 15. what number am... (answered by checkley77)

i have four digits. my ones digits is 4 more than my thousands digits. my hundreds digits (answered by richard1234)