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P(<em>X</em> ≤ 65) = P((<em>X</em> - 79)/7 ≤ (65 - 79)/7) = P(<em>Z</em> ≤ -2)
where <em>Z</em> follows the standard normal distribution with mean 0 and standard deviation 1.
Recall that for any normal distribution with mean <em>µ</em> and s.d. <em>σ</em>, we have
P(|<em>X</em> - <em>µ</em>| ≤ 2<em>σ</em>) ≈ 0.95
which in the case of <em>Z</em> translates to
P(-2 ≤ <em>Z</em> ≤ 2) ≈ 0.95
Now,
P(-2 ≤ <em>Z</em>) + P(-2 ≤ <em>Z</em> ≤ 2) + P(<em>Z</em> ≥ 2) = 1
==> P(-2 ≤ <em>Z</em>) + P(<em>Z</em> ≥ 2) ≈ 0.05
Any normal distribution is symmetric about its mean, so P(-2 ≤ <em>Z</em>) = P(<em>Z</em> ≥ 2), and this gives us
==> 2 P(-2 ≤ <em>Z</em>) ≈ 0.05
==> P(-2 ≤ <em>Z</em>) ≈ 0.025
Solutions: x=3 , y=5 , z=2
x+y+z=10
2x-5y+2z=-15
4x+y-z=15
Answer:
55 grams
Step-by-step explanation:
11 × 5
for example: (five days)
Monday: 11g
Tuesday: 11g
Wednesday: 11g
Thursday:11g
Friday: 11g
add up all the 11's which equals 55