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A civil engineer involved in construction requires 5000, 6000, 6200 and 5462 m3

ID: 2941693 • Letter: A

Question

A civil engineer involved in construction requires 5000, 6000, 6200 and 5462 m3 of sand, find gravel, coarse gravel and additives respectively, for a building project. There are four pits from which these materials can be obtained. The composition of these pits is:

How many cubic meters must be hauled from Pit 3 in order to meet the engineer`s needs?

(Use any numerical methods-Any unknowns finding technique like gauss-seidel, LU decomposition and such)

A civil engineer involved in construction requires 5000, 6000, 6200 and 5462 m3 of sand, find gravel, coarse gravel and additives respectively, for a building project. There are four pits from which these materials can be obtained. The composition of these pits is: How many cubic meters must be hauled from Pit 3 in order to meet the engineer's needs? (Use any numerical methods-Any unknowns finding technique like gauss-seidel, LU decomposition and such)

Explanation / Answer

Misread 35 as 55 so I kept getting negative answers so I didn't use gauss originally. this should be accurate

Rewrite the matrix as its transpose and set it equal to 5000, 6000, 6200, and 5462 respectively

50 20 20 10 5000
30 40 10 15 6000
10 20 40 55 6200
10 20 30 40 5462

Divide row1 by 50
1     2/5     2/5     1/5     100
30     40     10     15     6000
10     20     40     35     6200
10     20     30     40     5462

Add (-30 * row1) to row2
1     2/5     2/5     1/5     100
0     28     -2     9     3000
10     20     40     35     6200
10     20     30     40     5462

Add (-10 * row1) to row3
1     2/5     2/5     1/5     100
0     28     -2     9     3000
0     16     36     33     5200
10     20     30     40     5462

Add (-10 * row1) to row4
1     2/5     2/5     1/5     100
0     28     -2     9     3000
0     16     36     33     5200
0     16     26     38     4462

Divide row2 by 28
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     16     36     33     5200
0     16     26     38     4462

Add (-16 * row2) to row3
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     0     260/7     195/7     24400/7
0     16     26     38     4462

Add (-16 * row2) to row4
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     0     260/7     195/7     24400/7
0     0     190/7     230/7     19234/7

Divide row3 by 260/7
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     0     1     3/4     1220/13
0     0     190/7     230/7     19234/7

Add (-190/7 * row3) to row4
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     0     1     3/4     1220/13
0     0     0     25/2     2606/13

Divide row4 by 25/2
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     0     1     3/4     1220/13
0     0     0     1     5212/325

Add (-3/4 * row4) to row3
1     2/5     2/5     1/5     100
0     1     -1/14     9/28     750/7
0     0     1     0     26591/325
0     0     0     1     5212/325

Add (-9/28 * row4) to row2
1     2/5     2/5     1/5     100
0     1     -1/14     0     232023/2275
0     0     1     0     26591/325
0     0     0     1     5212/325

Add (-1/5 * row4) to row1
1     2/5     2/5     0     157288/1625
0     1     -1/14     0     232023/2275
0     0     1     0     26591/325
0     0     0     1     5212/325

Add (1/14 * row3) to row2
1     2/5     2/5     0     157288/1625
0     1     0     0     70091/650
0     0     1     0     26591/325
0     0     0     1     5212/325

Add (-2/5 * row3) to row1
1     2/5     0     0     104106/1625
0     1     0     0     70091/650
0     0     1     0     26591/325
0     0     0     1     5212/325

Add (-2/5 * row2) to row1
1     0     0     0     6803/325
0     1     0     0     70091/650
0     0     1     0     26591/325
0     0     0     1     5212/325

So in order to get the amount in Pit 3 we just take the third row which is 81.818 but this must be multiplied by a factor of becuase we solve in percentages:

8181.8 m3

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