- A30
- B60
- C33
- D27
Step-by-Step Solution
Let notebook = , pen = and . Multiply first by 2: . Subtract second: → .
Answer: A) 30
Riya bought 3 notebooks and 2 pens for ₹120. Her friend bought 2 notebooks and 4 pens for ₹120. Find the cost of one notebook (in rupees).
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
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