3-4 Systems of Equations in Three Variables Solve each system of equations. 3. SOLUTION:
Eliminate one variable. Multiply the second equation by –2 and add with the third equation.
Multiply the first equation by 2 and add with the second equation.
Solve the fifth and fourth equations.
Substitute 3 for y in the fourth equation and solve for x.
Substitute –4 for x and 3 for y in the second equation, and solve for z.
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Therefore, the solution is (–4, 3, 6).
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3-4 Systems of Equations in Three Variables
Therefore, the solution is (–4, 3, 6).
5. SOLUTION:
Eliminate one variable. Multiply the first equation by 2, multiply the second equation by 3 and add.
Multiply the second equation by 2 and add with the third equation.
Multiply the first equation by –4, multiply the third equation by 3, and add.
Since the equations 4, 5 and 6 are same, the system of equations has an infinite number of solutions. 7. DOWNLOADING Heather downloaded some television shows. A sitcom uses 0.3 gigabyte of memory; a drama, 0.6 gigabyte; and a talk show, 0.6 gigabyte. She downloaded 7 programs totaling 3.6 gigabytes. There were twice as many episodes of the drama as the sitcom. a. Write a system of equations for the number of episodes of each type of show. b. How many episodes of each show did she download? SOLUTION: a. Let s, t and d be the number of sitcoms, talk shows and dramas respectively. The system of equations is:
b. Solve eSolutions Manual - Powered by Cognero
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3-4 Systems of Equations in Three Variables Since the equations 4, 5 and 6 are same, the system of equations has an infinite number of solutions. 7. DOWNLOADING Heather downloaded some television shows. A sitcom uses 0.3 gigabyte of memory; a drama, 0.6 gigabyte; and a talk show, 0.6 gigabyte. She downloaded 7 programs totaling 3.6 gigabytes. There were twice as many episodes of the drama as the sitcom. a. Write a system of equations for the number of episodes of each type of show. b. How many episodes of each show did she download? SOLUTION: a. Let s, t and d be the number of sitcoms, talk shows and dramas respectively. The system of equations is:
b. Solve
.
Substitute 2s for d in the first and third equation.
Solve the fourth and fifth equations.
Substitute 2 for s in the second equation and solve for d.
Substitute 2 for s and 4 for d in the first equation and solve for t.
Therefore, she downloaded 2 episodes of sitcom, 4 episodes of drama and 1 episode of talk show. Solve each system of equations. eSolutions Manual - Powered by Cognero 9.
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Therefore, downloaded 2 episodes of sitcom, 4 episodes of drama and 1 episode of talk show. 3-4 Systems ofshe Equations in Three Variables Solve each system of equations. 9. SOLUTION:
Eliminate one variable. Multiply the third equation by 4 and add the first equation with that.
Multiply the third equation by –3 and add the second equation with that.
Solve the fourth and fifth equations.
Substitute –2 for b in the fifth equation and solve for c.
Substitute –2 for b and –4 for c in the third equation and, solve for a.
Therefore, the solution is (–3, –2, –4). eSolutions Manual - Powered by Cognero
11.
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3-4 Systems of Equations in Three Variables Therefore, the solution is (–3, –2, –4).
11. SOLUTION:
Eliminate one variable. Multiply the first equation by –4 and add with the second equation.
Multiply the third equation by 2, and add with the second equation.
Solve the fourth and fifth equations
.
Substitute –2 for r in the fifth equation and solve for s.
Substitute –2 and –1 for r and s in the first equation and solve for t.
Therefore, the solution is (–2, –1, 4). eSolutions Manual - Powered by Cognero
13.
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3-4 Systems of Equations in Three Variables Therefore, the solution is (–2, –1, 4).
13. SOLUTION:
Eliminate one variable. Add the first and the third equations.
Multiply the first equation by 3 and add with the second equation.
Multiply the third equation by –3 and add with the second equation.
Since the equations 4, 5 and 6 are same, the system has an infinite number of solutions. 21. AMUSEMENT PARKS Nick goes to the amusement park to ride roller coasters, bumper cars, and water slides. The wait for the roller coasters is 1 hour, the wait for the bumper cars is 20 minutes long, and the wait for the water slides is only 15 minutes long. Nick rode 10 total rides during his visit. Because he enjoys roller coasters the most, the number of times he rode the roller coasters was the sum of the times he rode the other two rides. If Nick waited in line for a total of 6 hours and 20 minutes, how many of each ride did he go on? SOLUTION: Let x, y and z be the number of raids in roller coaster, bumper car and water slide respectively. Nick rode 10 rides during his visit.
The number of times that Nick rode the roller coaster is the sum of the times he rode the other two rides. So:
He waited in line for a total of 6 hours 20 minutes. eSolutions Manual - Powered by Cognero
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The number of times that Nick rode the roller coaster is the sum of the times he rode the other two rides. So: 3-4 Systems of Equations in Three Variables
He waited in line for a total of 6 hours 20 minutes.
Substitute x for y + z in the first equation and solve for x.
Substitute 5 for x in the second and the third equation and simplify.
Multiply the fifth equation by –3 and add with the fourth equation.
Substitute 1 for y in the fifth equation and solve for z.
Nick rode the roller coaster, bumper cars and water slides 5, 1 and 4 times respectively. 24. CCSS REASONING Write a system of equations to represent the three rows of figures below. Use the system to find the number of red triangles that will balance one green circle.
SOLUTION: t + c = s, p + t = c, 2s = 3p where t represents triangle, c represents circle, s represents square, and p represents pentagon; 5 red triangles eSolutions Manual - Powered by Cognero
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3-4 Systems of Equations in Three Variables Nick rode the roller coaster, bumper cars and water slides 5, 1 and 4 times respectively. 24. CCSS REASONING Write a system of equations to represent the three rows of figures below. Use the system to find the number of red triangles that will balance one green circle.
SOLUTION: t + c = s, p + t = c, 2s = 3p where t represents triangle, c represents circle, s represents square, and p represents pentagon; 5 red triangles
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