Given "\\mu=100, \\sigma=10"
a.
"P(90<X<110)=P(X<110)-P(X\\leq90)""=P(Z<\\dfrac{100-100}{10})-P(Z\\leq\\dfrac{90-100}{10})"
"=P(Z<0)-P(Z\\leq-1)\\approx0.5-0.158655"
"=0.341345"
"0.341345(2000)=683"
683 students
b.
"P(80<X<120)=P(X<120)-P(X\\leq80)""=P(Z<\\dfrac{120-100}{10})-P(Z\\leq\\dfrac{80-100}{10})"
"=P(Z<2)-P(Z\\leq-2)\\approx0.977250-0.022750"
"=0.9545"
"0.9545(2000)=1909"
By the 68-95-99.7 rule
"0.9545(2000)=1909"
1909 students
c.
"P(X>130)=1-P(X\\leq130)""=1-P(Z\\leq\\dfrac{130-100}{10})=1-P(Z\\leq 3)"
"\\approx1-0.998650=0.00135"
"0.00135(2000)=3"
3 students
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