Currency note mix: A man has 170 currency notes consisting of ₹100 and ₹50 denominations totaling ₹10000. How much money is in ₹50 notes?

Difficulty: Easy

Correct Answer: ₹ 7000

Explanation:


Introduction / Context:
This is a standard system-of-equations problem involving two denominations. We know the total number of notes and the total value, and we must determine the value tied to one denomination (₹50 notes).


Given Data / Assumptions:

  • Total notes = 170
  • Denominations: ₹100 and ₹50
  • Total value = ₹10000


Concept / Approach:
Let x be the number of ₹100 notes and y be the number of ₹50 notes. Then x + y = 170 and 100x + 50y = 10000. Solve this linear system to find y and compute 50y.


Step-by-Step Solution:

x + y = 170 … (1)100x + 50y = 10000Divide value equation by 50: 2x + y = 200 … (2)(2) - (1): (2x + y) - (x + y) = 200 - 170 ⇒ x = 30Then y = 170 - 30 = 140Value in ₹50 notes = 50 * 140 = ₹7000


Verification / Alternative check:

Value in ₹100 notes = 30 * 100 = ₹3000Total = 3000 + 7000 = ₹10000 (consistent)


Why Other Options Are Wrong:

  • ₹ 4000: Implies only 80 fifty-rupee notes; would not total ₹10000 with 170 notes.
  • ₹ 9000: Exceeds the maximum possible given only 170 notes.
  • ₹ 6000: Leads to inconsistent counts with the total number of notes.


Common Pitfalls:

  • Forgetting to divide the value equation by 50 to simplify.
  • Arithmetic slips when subtracting equations.


Final Answer:

₹ 7000

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