If x/3 + y/4 = 7 and x/4 + y/3 = 8, what is the value of x + y?
Answer and explanation
Correct answer: 180/7
This is a pair of linear equations with fractional coefficients, so clearing the denominators is an efficient elimination step. Multiplying both equations by 12 gives 4x + 3y = 84 and 3x + 4y = 96. Adding these equations eliminates neither variable individually, but it directly produces 7x + 7y = 180. Dividing by 7 gives x + y = 180/7. Therefore, option B is correct. The nearby integer choices 24, 26, and 28 are not equal to 180/7; they could result from rounding or from an arithmetic error while adding the two equations.
Frequently asked questions
What is the correct answer to this question?
180/7
Why is this the correct answer?
This is a pair of linear equations with fractional coefficients, so clearing the denominators is an efficient elimination step. Multiplying both equations by 12 gives 4x + 3y = 84 and 3x + 4y = 96. Adding these equations eliminates neither variable individually, but it directly produces 7x + 7y = 180. Dividing by 7 gives x + y = 180/7. Therefore, option B is correct. The nearby integer choices 24, 26, and 28 are not equal to 180/7; they could result from rounding or from an arithmetic error while adding the two equations.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Pair of Linear Equations in Two Variables. Topic: Algebraic methods: Substitution method and Elimination method..
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