Pair of Linear Equations in Two Variables
RD Sharma
CBSE
Grade 10
Question:
If $217x + 131y = 913$ and $131x + 217y = 827$, then the value of $x + y$ is:
(a) $5$
(b) $6$
(c) $7$
(d) $8$
Step-by-Step Solution
Key Concept: Add both equations: $(217 + 131)x + (131 + 217)y = 913 + 827 \Rightarrow 348x + 348y = 1740 \Rightarrow x + y = 5$.
$348x + 348y = 1740 \Rightarrow x + y = 1740 / 348 = 5$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Adding equations and dividing by 348 to get $x + y = 5$: 1.0 Mark
Correct Answer: $5$
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