10th Class Mathematics Pair of Linear Equations in Two Variables Question Bank MCQs - Pair of Linear Equations in Two Variables

If \[\text{47x}+\text{31y}=\text{18}\]and \[\text{31x}+\text{47y}=\text{6}0,\] then value of \[\text{x}+\text{y}\]is:

A) 1

B) 0

C) 23

D) 47

Correct Answer: A

Solution :

[a] Given,

\[47x+31y=18\] ...(1)

and \[31x+47y=60\] ...(2)

Adding eqs. (1) and (2), we get

\[78x+78y=78\]

\[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x+y=1\] (divide both sides by 78)