- A₹10
- B₹25
- C₹15
- D₹20
Step-by-Step Solution
Let pen=, book=. Multiply first by 2: . Subtract: .
Answer: A) ₹10
Cost of 3 pens and 2 books is ₹80. Cost of 5 pens and 4 books is ₹150. Find cost of one pen.
Class 10Pair of Linear Equations in Two VariablesAlgebra — Systems of Equations
Key idea: Word problems and translation
Most Class 10 questions on this topic are word problems. The skill is in TRANSLATION:
1. Identify the two unknowns; assign variables (e.g., let = age of A, = age of B).
2. Write two equations from the two given pieces of information.
3. Solve by your preferred method.
**Common types**:
- **Age problems**: 'Father is twice as old as son. Five years ago father was three times. Find ages.'
- **Number problems**: 'A two-digit number plus its reverse is 99...'
- **Distance/time/speed**: 'Boat in still water speeds, downstream/upstream rates...'
- **Cost problems**: 'Cost of pencils and pens.'
- **Fraction problems**: 'A fraction becomes 1/2 when 1 is added to numerator and 2 is subtracted from denominator...'
Always CHECK by substituting solution back into the original word problem (not just the equations).
1. Identify the two unknowns; assign variables (e.g., let = age of A, = age of B).
2. Write two equations from the two given pieces of information.
3. Solve by your preferred method.
**Common types**:
- **Age problems**: 'Father is twice as old as son. Five years ago father was three times. Find ages.'
- **Number problems**: 'A two-digit number plus its reverse is 99...'
- **Distance/time/speed**: 'Boat in still water speeds, downstream/upstream rates...'
- **Cost problems**: 'Cost of pencils and pens.'
- **Fraction problems**: 'A fraction becomes 1/2 when 1 is added to numerator and 2 is subtracted from denominator...'
Always CHECK by substituting solution back into the original word problem (not just the equations).
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Practice 5 Similar Questions Free →All Pair of Linear Equations in Two Variables practice questions
More Class 10 Pair of Linear Equations in Two Variables practice
A pair of linear equations in two variables is generally written as a1x + b1y + c1 = 0…A system of two linear equations that has no solution is called:For the pair 3x + 2y = 5 and 2x − 3y = 7, the lines:The graph of a pair of linear equations in two variables is a pair of:For what value of k do the lines 3x + 4y = 7 and 6x + 8y = k represent the SAME line?