难题
一、一个袋中装有2个黄球和2个红球,任意摸出一个球后放回,再任意摸出一个球,请和你的同伴合作,记录实验10次,50次,100次,150次,200次后,第一次摸到红球的次数n1,两次都摸到红球的次数n2.
试验次数n 10次 50次 100次 150次 200次
n1（频数）
n1/n（频率）
n2（频数）
n2/n（频率）
你们能发现什么现象?第一次摸到红球的概率估计值是多少?两次都摸到红球的概率估计多少?
二、 James gets up at five to seven.His parents and his little twin sisters go travelling in France and he has to look after himself at home.He opens the fridge,but he finds there are only two hamburgers in it.He decides to have breakfast in the restaurant on the other side of the street.He sits at a table,the waiter comes up and says ,"Can I take your order,James?"
But you don't show your menu(菜单) to me,Mr Hunt."says the boy.
"Oh,sorry!I forget it.Here it is."
James looks at the menu carefully.
Bread ￥1.30 Sandwich ￥1.80 Hamburger ￥2.00 Pizza ￥2.40
Egg ￥0.30 Milk ￥0.50 Coffee ￥0.70 Coke ￥0.30
James takes out his wallet and finds there is only 6.50 yuan in it.
"Well."says Mr Hunt."What about a hamburger,a pizza,two eggs and a glass of Coke?"
"Oh,no."says the boy."I will buy a picture-book this afternoon.It's 1.50 yuan."
"I see,"says the waiter.And then he brings the boy a nice breakfast.
根据短文内容,完成下列句子,每格所填词数不限
1、hopes to pay ________ for his breakfast.
2、James maybe has two eggs,a pizza,a cup of coffee and a piece of bread for _________.
希望回答者能给出答案的理由.
数学题目中“第一次摸到红球的次数n1,两次都摸到红球的次数n2”这句话是什么意思?否则没法填表格啊