### Brain Teasers

# Matrix+Matrix

Situation
Situation puzzles (sometimes called lateral thinking puzzles) are ones where you need to ask lots of yes or no questions to figure out what happened in the situation. These are good puzzles for groups where one person knows the puzzle and answers the questions.

1. The math teacher gave Pat two matrices and told her to add them. But she said she couldn't add them even though she learned how to do matrix addition the day before. The funny thing is that the teacher said that she did a good job. Why?

2. The math teacher then gave Mat two matrices and told him to add them. This time, Mat added them and showed the results to the teacher. But the teacher looked at him strangely. Why?

2. The math teacher then gave Mat two matrices and told him to add them. This time, Mat added them and showed the results to the teacher. But the teacher looked at him strangely. Why?

### Hint

dimensions### Answer

You have to understand about dimensions in a matrix in order to solve this teaser. Each matrix has its own dimension, and it's determined by the number of rows and columns of numbers in it. You can add or subtract matrices only when they have same dimensions.1. The two matrices had different dimensions. So, it was impossible to add. Therefore, you are right if you say you cannot add them.

2. The teacher gave him matrices with different dimensions, too. But he somehow added them even though it is not possible!

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