My course work in maths is going to consist of opposite corners and/or hidden faces.
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Introduction
My course work in maths is going to consist of opposite corners and/or hidden faces. For my first course in mathematics I have been given the task of investigating the difference between the products of the numbers in the opposite corners of my rectangle that can be drawn on a 10 by 10 square.
I will start off by showing some examples of different rectangles and what the sum of the corners will be. This will help me to determine whether or not there is a pattern.
Example
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 |
91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
1* 12=12
2* 11=22
22-12=10
This example shows us that between the squares 1,2,11,12 the sum will be 10.
We will now go on to see what a square between 1,2,21,22 will be.
Middle
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
3*14=42
4*13=52
52-42=10
For now it seems as though the pattern is working the same for the rest of the table. We need to justify our conclusion by drawing another two examples.
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 |
91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
3*24=76
4*23=96
96-76 = 20
Again the same results seem to be occurring in this row but to be sure we will do one more example.
Example
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 |
91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
3*34= 102
4*33= 132
132 – 102 = 30
As is confirmed by my results any rectangle that is 2 along and 2 down will be 10, then 2 along 3 down will be 20 and so on and so forth.
Now that we have a small result
Conclusion
Example
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 |
91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
1*33=33
3*31=93
93-33=60
This confirms my prediction.
Now that I have gathered some information I can create I table of my results
and of further predictions.
2*2=10 | 3*2=20 | 4*2=30 | ||
2*3=20 | 3*3=40 | 4*3=60 | ||
2*4=30 | 3*4=60 | 4*4=90 | ||
2*5=40 | 3*5=80 | 4*5=120 | ||
2*6=50 | 3*6=100 | 4*6=150 | ||
2*7=60 | 3*7=120 | 4*7=180 | ||
2*8=70 | 3*8=140 | 4*8=210 | ||
2*9=80 | 3*9=160 | 4*9=240 | ||
2*10=90 | 3*10=180 | 4*10=270 |
I could carry on but I am sure that you can see from the table that a 5*2 would be 40 then a 5*3 would be 80 and so on.
Justification
The formula for the sum of the opposite corners minus the sum of the two opposite corners is :-
(10x – 10) * (y – 1)
X = the number of squares across
Y = the number of squares down
An example of this is a 3 * 3 square would equal
(10*3 – 10) * (3-1)
= 20 * 2
= 40
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 |
91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
If we work this out by multiplying the opposite corners and subtracted the sums we get
3 * 21 – 1 *23
= 63 – 23
= 40
This proves my formula works.
This student written piece of work is one of many that can be found in our GCSE Number Stairs, Grids and Sequences section.
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Here's what a teacher thought of this essay
The general pattern for a 10 x 10 grid is identified. To improve this investigation more algebraic manipulation is needed to verify the identified pattern. There should be multiplication of double brackets and the identification of an nth term. Specific strengths and improvements have been suggested throughout.
Marked by teacher Cornelia Bruce 18/04/2013