So, the number of nuclei, 119 if we were to sit and count these as well, is 119. So, we'll multiply that by just pi, r squared, to get that cross-section, and divide all of that by 1 .

如果你们数的话，原子核的数是，我们用它乘以πr的平方，得到横截面积，除以1。

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So, the number of nuclei, 119 if we were to sit and count these as well, is 119. So, we'll multiply that by just pi, r squared, to get that cross-section, and divide all of that by 1 . 39 meters squared.

如果你们数的话，原子核的数是，我们用它乘以πr的平方，得到横截面积，除以1。39平方米。

麻省理工公开课 - 化学原理课程节选

The draft primary curriculum for maths, due to be introduced in schools next year, contains plans for pupils to memorise their times tables up to 12 by age nine, multiply and divide fractions by age 11, as well as learn topics such as geometry, long division and multiplication and decimals.

BBC: Primary maths plan threatens 'too much too soon'