Normal distribution problem

Hi guys, i’m not sure if I’m supposed to be so precise but in this prepswift problem it says that 1/6 is appx 16%. But 1/6 is basically 17% when you round it. So then, I thought 40 cannot be the exact boundary of the mean minus 1 SD. Because it’s basically a bit above it.

I know it says approximation but because I’m trying to understand it well enough for a good score, i just need to know if it makes sense what I’m saying. What I thought was the following (but that would mean ignoring some of the info)

1.48 times the mean = 70
so the mean is 70/1.48 which is appx 47

thanks for helping out

It’s just an approximation; the question asks for an estimate for the mean.
(also: 1/6 is closer to 16% than 17%)