Question 1174170
the 10th percentile is z=-1.28
z=(x-mean)/sd
-1.28=(200-mean)/7.8
200-mean=-9.98
mean=209.98 or 210 gm.
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>225 gm would be a z> 15/7.8 or 1.92. That probability is 0.0274
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between 215 and 230 would be a z of between 5/7.8 and 20/7.8 or 0.64 and 2.56
probability is 0.2559
or calculator 2nd VARS 2 normalcdf(215,230,210,0.78) ENTER 0.2556 (less rounding than above)