3 The amount of fibre in a packet of a certain brand of cereal is normally distributed with mean 160 grams. 19\% of packets of cereal contain more than 190 grams of fibre.
- Find the standard deviation of the amount of fibre in a packet.
- Kate buys 12 packets of cereal. Find the probability that at least 1 of the packets contains more than 190 grams of fibre.