Final answer:
The missing number in the sequence is 320.
Step-by-step explanation:
The missing number in the sequence is 320. To find the missing number, we can divide the first number, 640, by the second number, 2.5. This will give us 256. Since we are missing a number between 640 and 2.5, we need to find the average of these two numbers, which is found by adding them together and dividing by 2. Thus, the missing number is 320.
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