小弟求解

2.A sakesman has a 30% probability of making a sale to any customer. Assume all customers are independent of one another.

Question: What is the probability the first sale is made to the third customer? what is the probability the first four customers do not purchase the product?

第一题的意思是前两次都没卖出,第三次卖出了,概率是: 0.7*0.7*0.3=0.147

第二题前四次都没卖出，概率是：0.7^4=0.2401