74. The probability that the total length of flax plants of variety $A$ is $75-84$ cm is 0.6. What is the probability that among 300 flax plants of this variety, the relative frequency of plants of such length will deviate in absolute value from the probability of the appearance of plants of such length by no more than 0.05?
The problem is solved. According to the conditions $n=300 ; \varepsilon=0.05, p=0.6$; we find $q=0.4$.

The required probability will be found using formula (23):

$$
P\left(\left|\frac{m}{n}-0.6\right| \leq 0.05\right) \approx 2 \Phi\left(0.05 \sqrt{\frac{300}{0.6 \cdot 0.4}}\right) \approx 2 \Phi(1.77)=2 \cdot 0.4616=0.9232
$$