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。
Children should be able to add and subtract in the third grade. By the end of fifth grade, they should be able to multiply and divide.
孩子们应该在三年级能够进行加、减法运算,在五年级结束时能够进行乘、除法运算。
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。
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