Agree with all the above. I loath the numerical ones and only tackle them to stay in the annual ratings. So thanks for such a simple one. Lets have more of them like this! 30 minutes start to finish. Like most (all?) arithmetic ones, this one was devoid of pdm's.
Back when they moved the numerics back/forward a week I suggested it was because someone wanted a particular number for their crossword - is this it?