1. **Problem 1:** Find the probability that a child picked at random has a height greater than 104cm.
Given: $X=104$, $\mu=110$, $\sigma=5$
Formula: Use the standard normal distribution $Z=\frac{X-\mu}{\sigma}$.
Calculate $Z$:
$$Z=\frac{104-110}{5}=\frac{-6}{5}=-1.2$$
Find $P(X>104)=P(Z>-1.2)$.
Using standard normal tables or symmetry:
$$P(Z>-1.2)=1-P(Z\leq -1.2)=1-0.1151=0.8849$$
So, the probability is approximately 0.8849.
2. **Problem 2:** Find the probability that the height of a child picked at random is less than 116cm.
Given: $X_1=116$, $\mu=110$, $\sigma=5$
Calculate $Z$:
$$Z=\frac{116-110}{5}=\frac{6}{5}=1.2$$
Find $P(X<116)=P(Z<1.2)$.
From standard normal tables:
$$P(Z<1.2)=0.8849$$
So, the probability is approximately 0.8849.
3. **Problem 3:** Find how many children are between 98cm and 122cm.
Given: $X=98$, $X_2=122$, $\mu=110$, $\sigma=5$
Calculate $Z$ values:
$$Z_1=\frac{98-110}{5}=\frac{-12}{5}=-2.4$$
$$Z_2=\frac{122-110}{5}=\frac{12}{5}=2.4$$
Find $P(98 X_c) = 0.15$.
Find $Z_c$ such that $P(Z > Z_c) = 0.15$.
From standard normal tables, $Z_c \approx 1.04$.
Calculate $X_c$:
$$X_c=\mu + Z_c \times \sigma = 110 + 1.04 \times 5 = 110 + 5.2 = 115.2$$
Number of children:
$$500 \times 0.15 = 75$$
**Final answers:**
1. Probability height $>$ 104cm is approximately 0.8849.
2. Probability height $<$ 116cm is approximately 0.8849.
3. Number of children between 98cm and 122cm is approximately 492.
4. Number of children in the upper 15% is 75.
Height Probabilities 9F92E2
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