Problem
COM-B1-M04-P003 Rows and Columns
#3
★☆☆☆☆ Level 1 of 5
A table contains numbers. Explain why the sum of row sums equals the sum of column sums.
Each cell is counted exactly once in both counts.
When summing by rows, each entry is counted once. When summing by columns, each entry is also counted once. Therefore the totals are equal.
Fundamental double-counting idea.