The task is to generate the correct answer for a given math problem.

Q: Problem: two pipes can fill the cistern in 10 hr and 12 hr respectively , while the third empty it in 30 hr . if all pipes are opened simultaneously , then the cistern will be filled in

A: 6.67 hr
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Q: Problem: what is the greatest prime factor of 2 ^ 10 - 1 ?

A: 3
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Q: Problem: evaluate : 2.5 + 0.0005

A:
5000
****