SOLUTION: Lengths of a certain type of white radish are normally distributed with mean x cm and standard deviation y cm. 4% of these radishes are longer than 12 cm and 32% are longer than 9

Question 1082057: Lengths of a certain type of white radish are normally distributed with mean x cm and standard
deviation y cm. 4% of these radishes are longer than 12 cm and 32% are longer than 9 cm. Find x and y.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
4% is at z=+1.75
32% is at z=+0.47
1.75=(x-mean)/y, but x-mean=12-mean
1.75y=12-mean
mean+1.75y=12 and similarly,
mean+0.47y=9
subtract second
1.28y=3
y=2.34 cm
mean+1.10=9
mean=7.9 cm
check with first
7.9+1.75(2.34)=11.995, 12 with rounding error
x=7.9 cm
y=2.34 cm

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