alleryFrom 2x + y = 7 and x + y = 4, the value of y is
- 4
- 2
- 3
- 1
Show answer and solution
Correct answer: D. 1
Subtracting gives x = 3, and then y = 4 - 3 = 1.
RRB NTPC Elementary Algebra — practice questions — page 2
Explore 67 free Elementary Algebra questions in RRB NTPC Mathematics. Open each question or exercise to read its content, reference answers and available explanation.
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Showing questions 31–60 of 67.
From 2x + y = 7 and x + y = 4, the value of y isRead the answer and worked solution →Two pens and a pencil cost Rs 25; a pen and two pencils cost Rs 20. One pen costsRead the answer and worked solution →A rectangle is 4 cm longer than wide and has perimeter 40 cm. Its length isRead the answer and worked solution →Adding x + y = 7 and x - y = 3 eliminates which variable?Read the answer and worked solution →Two linear equations whose graphs are parallel lines haveRead the answer and worked solution →Two equations that represent the same line giveRead the answer and worked solution →Two lines meeting at exactly one point mean the system hasRead the answer and worked solution →A linear system that has no solution is calledRead the answer and worked solution →In three variables, each linear equation represents aRead the answer and worked solution →An inconsistent system can always be reduced to the false statementRead the answer and worked solution →Algebra differs from arithmetic mainly by introducingRead the answer and worked solution →The rule a + b = b + a is called theRead the answer and worked solution →Substituting a = 3 in the expression 5a givesRead the answer and worked solution →If x = 4, the value of 2x^2 + 3 isRead the answer and worked solution →Completing the square is used to derive theRead the answer and worked solution →If an equation is written as E times F equals 0, solving it reduces to solvingRead the answer and worked solution →An equation states that two expressions areRead the answer and worked solution →Solve 2(x + 3) = 3x - 1.Read the answer and worked solution →Solve 3x - 4 = 5x + 6.Read the answer and worked solution →Five years ago a mother was thrice her son's age; now their ages sum to 50. The son isRead the answer and worked solution →A two-digit number has digit sum 9 and grows by 27 when reversed. The number isRead the answer and worked solution →A single linear equation in two variables hasRead the answer and worked solution →By definition, equality is what kind of mathematical relation?Read the answer and worked solution →In elementary algebra, like terms in a sum are simplified by combining which values?Read the answer and worked solution →Which algebraic law justifies extracting a common factor from multiple terms?Read the answer and worked solution →How many possible categories of solution sets can a linear system exhibit?Read the answer and worked solution →What geometric entity does a linear equation in two variables x and y determine?Read the answer and worked solution →In three-dimensional space, what geometric object does a single linear equation represent?Read the answer and worked solution →In elementary algebra, what term designates letters used to represent non-specified numbers?Read the answer and worked solution →When a system of two lines on the plane has no intersection, what is its solution set?Read the answer and worked solution →
Worked practice questions
Two pens and a pencil cost Rs 25; a pen and two pencils cost Rs 20. One pen costs
- Rs 12
- Rs 10
- Rs 5
- Rs 15
Show answer and solution
Correct answer: B. Rs 10
Let a pen cost $p$ and a pencil cost $q$. Then $2p+q=25$ and $p+2q=20$. Double the first equation and subtract the second: $(4p+2q)-(p+2q)=50-20$, giving $3p=30$ and $p=10$. A pen costs Rs 10 (option B).
A rectangle is 4 cm longer than wide and has perimeter 40 cm. Its length is
- 8 cm
- 10 cm
- 12 cm
- 16 cm
Show answer and solution
Correct answer: C. 12 cm
Length plus breadth is 20 and their difference is 4, so length is 12 cm.
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