Question

i am a 3 digit number,my ones digit is twice my hundreds digit,when rounded to the nearest hundred i round to 500,my tens digit is less than 6,what number am i?

Answer 1

Suppose the number is ABC. Then if C is twice A, we know that A can't be any greater than 4. So the number must be one of the following: 1B2, 2B4, 3B6 or 4B8. When rounded to the nearest hundred it's 500, so it must be the last of those four, i.e. 4B8. If the tens digit is less than 6 then the number must be 408, 418, 428, 438, 448 or 458. All of these would round to 400 except the last one, so the answer must be 458.