Suppose "X" is a variable representing the mass of the packet of milk powder. "X" is normally distributed with mean of 650 g and standard deviation of 10 g:
If "X\\sim N(\\mu, \\sigma^2)", then "Z={X-\\mu \\over \\sigma}\\sim N(1, 0)"
The probability that a packet selected at random will have a mass between 620g and 655g
If 500 packets are selected at random, how many of them will have a mass of more than 660g?
Given that "N=500."
"P(X>660)=P(Z>{660-650 \\over 10})=1-F(1)=""=1-0.841345=0.158655""n=N\\cdot P(X>660)=500\\cdot 0.158655=79"It is found that 10% of packets of milk powder will have a mass of less than k .
"k=650-10\\cdot1.281552\\approx637"
The probability that a packet selected at random will have a mass between 620g and 655g is "0.690112."
If 500 packets are selected at random, then 79 of then will have a mass of more than 660g.
It is found that 10% of packets of milk powder will have a mass of less than k=637 g .
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