Maths : Basic Numeracy

Q 79 / 370

UPSC CSE Prelims 2024

A person buys three articles P, Q and R for ₹ 3,330. If P costs 25% more than R and R costs 20% more than Q, then what is the cost of P?

EXPLANATION

Correct Option (4)

Let the cost of article Q be x.

  • Article R costs 20% more than Q. Therefore, the cost of R is x+0.20x=1.2x=6x5.
  • Article P costs 25% more than R. Therefore, the cost of P is R+0.25R=1.25R=54R.
  • Substituting the value of R: Cost of P =54×6x5=30x20=3x2.

The total cost of the three articles is ₹ 3,330. Thus, the sum of their costs is:

3x2+x+6x5=3330

To solve for x, find a common denominator (10):

15x10+10x10+12x10=3330

15x+10x+12x10=3330

37x10=3330

37x=3330×10

37x=33300

x=3330037=900

This value represents the cost of article Q (₹ 900).

The cost of article P is 3x2:

Cost of P =3×9002=27002=1350

Therefore, the cost of P is ₹ 1,350.

Incorrect Options:

  • Options 1 (₹ 1,000), 2 (₹ 1,200), and 3 (₹ 1,250) are incorrect. If any of these values were the cost of P, the corresponding costs for Q and R, derived from the given percentage relationships, would not sum up to the total purchase price of ₹ 3,330. These values are inconsistent with the established proportional relationships between the articles' costs and their aggregate sum.