报童购进数量应根据需求量确定，但需求量是随机的，所以报童每天如果购进的报纸太少，不够买的，会少赚钱；如果购进太多，卖不完就要赔钱，这样由于每天报纸的需求量是随机的，致使报童每天的收入也是随机的，因此衡量报童的收入，不能是报童每天的收入，而应该是他长期（几个月、一年）卖报的日平均收入。我们可以应用计算机模拟的方法 在模拟时间充分大的条件下（例如10000天），模拟每天的销售量，因而确定每天应买进多少报纸才能使平均总收入达到最大值。(The number of paper purchased should be determined according to the demanded. But the demand is random. So the newsboy will get less money if he buys too few or too much newspapers. The newsboy's daily income is random. Therefore, the income of newsboy cannot be measured by the income of a day, and should be his long term (one year) average income.We can use of the method of computer simulation while the condition of simulation time is sufficiently large (10000 days for example), simulate daily sales, and thus determine how much to buy every day to get the maximum average revenue.)