So you should have gotten two handouts as you came in, and if you didn't, please raise your hand and a TA will come to you and get you that second handout.

因此你们应该都在进来的时候拿到了两份讲义，如果你没有，请举手示意，助教会过去,给你第二份讲义。

麻省理工公开课 - 化学原理课程节选

We know we need to divide by 266, 266 but what we need you to help us with is to figure out this top number here and see how many particles are going to backscatter. So if the TAs can come up and quickly hand out 1 particle to everyone.

知道背散射的概率就可以了，我们知道要除以,但还需要你们来搞清楚,分子上的数是多少，有多少个发生背散射的粒子,助教们请过来,把这些球分给同学们。

麻省理工公开课 - 化学原理课程节选

We have 266 ping-pong balls, and we need someone, hopefully you, to be some radioactive material that are going to be emitting these ping-pong balls. And when the time comes, in just a minute, I'll ask the TAs to come down and hand these out very quickly to you, so we can do this experiment.

你们有些人那天，看到我在办公室数乒乓球，我们需要几个人,希望是你,来作为放射材料，放射这些乒乓球,等会我会让助教,把这些球发给你们。

麻省理工公开课 - 化学原理课程节选