For a second photograph，the members stand in two rows，with 6 on the back row and 4 on the front row．Olly and his sister Petra are two of the members of the club．
在第二张照片中，成员们站成两排，后排 6 人，前排 4 人。
（c）How many different arrangements are there of the 10 members in which Olly and Petra stand next to each other on the front row？
（c）Olly 和 Petra 并排站在前排的 10 名成员中，有多少种不同的安排？
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（a）The lengths，in centimetres，of middle fingers of women in Raneland have a normal distribution with mean $\mu$$\mu$mu\mu and standard deviation $\sigma$$\sigma$sigma\sigma ．It is found that $25\mathrm{\%}$$25\mathrm{\%}$25%25 \% of these women have fingers longer than 8.8 cm and $17.5\mathrm{\%}$$17.5\mathrm{\%}$17.5%17.5 \% have fingers shorter than 7.7 cm ．
（a）Raneland 妇女的中指长度（以厘米为单位）呈均值 $\mu$$\mu$mu\mu 和标准差的正态分布 $\sigma$$\sigma$sigma\sigma ， $25\mathrm{\%}$$25\mathrm{\%}$25%25 \% 发现这些妇女的手指长度超过 8.8 厘米， $17.5\mathrm{\%}$$17.5\mathrm{\%}$17.5%17.5 \% 手指短于 7.7 厘米。
（i）Find the values of $\mu$$\mu$mu\mu and $\sigma$$\sigma$sigma\sigma ．
（i） 求 $\mu$$\mu$mu\mu 和 $\sigma$$\sigma$sigma\sigma 的值。
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The lengths，in centimetres，of middle fingers of women in Snoland have a normal distribution with mean 7.9 and standard deviation 0.44 ．A random sample of 5 women from Snoland is chosen．
Snoland 女性的中指长度（以厘米为单位）呈正态分布，平均值为 7.9，标准差为 0.44 .从 Snoland 随机选择 5 名女性样本。
（ii）Find the probability that exactly 3 of these women have middle fingers shorter than 8.2 cm ．
（ii） 找出这些女性中正好有 3 个中指短于 8.2 厘米的概率。
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