If 6x - 5y = 8 and 9x + 10y = 83, what is the value of x + y?
Answer and explanation
Correct answer: 307/35
To eliminate y, multiply 6x - 5y = 8 by 2, obtaining 12x - 10y = 16. Add this to 9x + 10y = 83. The y terms cancel and give 21x = 99, so x = 33/7. Substitute this into the first equation: 6(33/7) - 5y = 8, hence 198/7 - 5y = 56/7 and 5y = 142/7. Thus y = 142/35. Therefore x + y = 33/7 + 142/35 = 165/35 + 142/35 = 307/35. Option B is correct. The integer options 8, 9, and 10 are only rough numerical neighbours and are not the exact value.
Frequently asked questions
What is the correct answer to this question?
307/35
Why is this the correct answer?
To eliminate y, multiply 6x - 5y = 8 by 2, obtaining 12x - 10y = 16. Add this to 9x + 10y = 83. The y terms cancel and give 21x = 99, so x = 33/7. Substitute this into the first equation: 6(33/7) - 5y = 8, hence 198/7 - 5y = 56/7 and 5y = 142/7. Thus y = 142/35. Therefore x + y = 33/7 + 142/35 = 165/35 + 142/35 = 307/35. Option B is correct. The integer options 8, 9, and 10 are only rough numerical neighbours and are not the exact value.
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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