S1 Solomon Paper D Help.

http://pmt.physicsandmathstutor.com/download/Maths/A-level/S1/Papers-Solomon/for-Edexcel/Solomon%20D%20QP%20-%20S1%20Edexcel.pdf

Part 6 a)

I've got the correct method but not the right answer because for some reason they got a Z value of -0.67 from the probability of 0.75 and I don't particularly understand why. The rest of my working is correct it's just this one section that's thrown me off.

[I also had trouble with question 5 c) but that is mainly because I don't understand why they've added the probabilities, i'm probably gonna look at it later though.]

Thanks!

The z values for diameters below the mean are negative, and for diameters above the mean it is positive. Since $P(D>2)=0.75$ and 2 is below the mean, its z value will be negative.

Thanks but I understand why it's negative, it's just where the 0.67 comes from, it doesn't make sense when looking at the tables as I can't seem to find anywhere where the value of 0.75 for probability can result with a 0.67.

:s

AQA's formula booklet