Consider the series: 635, 665, 620, 618, 648, ... Determine the next number in the sequence.

To determine the next number in the sequence, let's analyze the pattern.

Looking at the given numbers: 635, 665, 620, 618, 648, we can observe the following:

1. The first number, 635, increases by 30 to give the second number, 665.
2. The second number, 665, decreases by 45 to give the third number, 620.
3. The third number, 620, decreases by 2 to give the fourth number, 618.
4. The fourth number, 618, increases by 30 to give the fifth number, 648.

Based on this pattern, we can conclude that the sequence alternates between adding 30 and subtracting 45.

To find the next number, we need to continue this pattern.

The fifth number, 648, decreases by 45 to give the sixth number.

648 - 45 = 603

Therefore, the next number in the sequence is 603.