Step-by-step explanation:

Let's break down the clues given in the problem:

The last digit is twice the 2nd digit.

The 2nd digit is 1/4 of the math exam day, which means it must be either 1 or 4, as those are the only digits that are divisible by 4.

The 1st digit is the last digit of the total of the odd numbers less than 10. The odd numbers less than 10 are 1, 3, 5, 7, and their sum is 16. So the 1st digit is 6.

Putting these clues together, we know that the 2nd digit must be 4, since it's the only digit that is divisible by 4. Therefore, the last digit must be 8 (twice 4). And the 1st digit is 6.

So the number is 648.