Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
This topic is locked. If you want to discuss this question please re-post it in the respective forum.
Would anybody have a formula/explanation for this:
"Of the three-digit integers greater than 700, how many have two digits that are equal to each other and the remaining digit different from the other two?"
Could you explain this more? I am not sure to get it
8xx where x = 0~7, 9 - 9 of them 8x8 where x = 0~7, 9 - 9 of them 88x where x = 0~7, 9 - 9 of them
8xx where x = 0~7, 9 - 9 of them -> Keep the 8 fixed and make the ten's and unit's digits the same. For example, 800, 811, 822, etc. However, you cannot have 8xx where x = 8 since then, there would be 3 (not 2) identical numbers.
8x8 where x = 0~7, 9 - 9 of them -> Keep the hundred's and unit's digits fixed and rotate the middle digits.
88x where x = 0~7, 9 - 9 of them -> Keep the first two digits fixed and rotate the last digits.