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Notes for Lesson 12 – 1: Organizing Data Using Matrices Vocabulary: Matrix – A rectangular arrangement of numbers in rows and columns Element – Each number in a matrix Scalar – A real number used for multiplying a matrix Scalar Multiplication – An operation that multiplies a matrix by a scalar A matrix is a rectangular arrangement of data in rows and columns. You identify the size of a matrix by the number of row and the number of columns. So for the following matrix it would be a 3 x 2 because it has 3 rows and 2 columns. 5 1 2 0 3 4 Matrices are used to organize data and make it easier to perform calculations on the data 12-1.1 – Adding and subtracting matrices You may need to add or subtract matrices in order to solve problems. You can only add or subtract matrices that are the same size. You then add or subtract the matrices by adding or subtracting corresponding elements. Examples: −8 −1.2 −5 2.7 −3 −3.9 [ ]+[ ]=[ ] 3 −1 −4 2 7 −3 2 11 −1 8 3 3 [−4 3.2] − [−6.5 4 ] = [2.5 −0.8] 1.5 −5 0 −3 1.5 −2 12.1-2 – Multiplying a matrix by a scalar You may also need to multiply a matrix by a real number in order to solve a problem. The real number multiplier is called a scalar. Multiplying a matrix by this scalar is called scalar multiplication. To multiply a matrix by a scalar, distribute the scalar to each element in the matrix. Examples: 3[ 4 −1.5 12 ]=[ 1 −6 3 −4.5 ] −18 4 0 −2 [ −2 1 −8 0 5 ]=[ 4 −2 2 −10 ] −4 If you have a combination of multiplication and addition/subtraction remember in the order of operations that multiplication comes first. 3 0 6 0 6 −5 6 −5 0 [0 3 ] − 2 [−1 4] = [ 0 3 ] − [ −2 8] = [ 2 −6 2 −12 4 10 −2 1 −2 1 −5 −5] −3 12.1-3 – Using Matrices Which city has the greatest average number of clear days in a full year? Sept-Feb Clear Cloudy 102 41 [ 43 58] + 55 82 March-Aug Total Clear Cloudy 110 27 [ 31 59] = 45 83 Clear Cloudy 212 68 [ 74 117] 100 165 So, Phoenix has the most clear days with 212. Portland the most cloudy with 165. 892 351 739 215 153 136 46 ] so 166 more students played soccer among students. ⌈1114 483⌉ − [1023 437] = [ 91 −37 6 653 64 690 58 166 −5 1712 37 1546 42