I'd be entirely put off by someone who prefers to spend 5 seconds to give some (probably wrong) estimate rather than spending 10 seconds to punch in an expressi

I'd be entirely put off by someone who prefers to spend 5 seconds to give some (probably wrong) estimate rather than spending 10 seconds to punch in an expression providing the correct answer on the giant calculating machine they're either way sitting in front of. If I was asked during an interview, I'd either type it into the machine or write the calculation on the whiteboard and tell that there's absolutely no reason for me to concern myself with performing calculations when my job is literally to instruct machines to perform them.