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Meera's total marks in Mathematics and Science add up to 30. Had she scored 2 marks more in Mathematics and 3 marks less in Science, the product of the two marks would have been 210. What are the possible Mathematics marks?

Class 10Quadratic EquationsAlgebra — Quadratics
  • A13 only
  • B12 or 18
  • C17 or 18
  • D12 or 13

Step-by-Step Solution

Let Mathematics = , so Science . Then → → → → , so or 13. BOTH work: 12 and 18 give , and 13 and 17 give . Reporting "13 only" throws away an equally valid root — a root may only be rejected when the CONTEXT forbids it, and both marks here are legal. "12 or 18" mixes one subject with the other; "17 or 18" gives the Science marks.
Answer: D) 12 or 13

Key idea: Word problems with quadratics

Many real-world problems lead to quadratics:

**Number problems**: 'Find two consecutive integers whose product is 132.' Let ; → → or −12. Both valid (or pick positive).

**Area problems**: 'A garden's length is 5 m more than its width. Area is . Find dimensions.'
Let width = . Length = → → (rejecting negative).

**Speed/time/distance**: 'A train takes 1 hour less if its speed is increased by 10 km/h. Original speed?' → typical setup: time1 − time2 = 1 → distance/speed equations → quadratic in speed.

**Always**: reject negative or extraneous roots if context demands positive (lengths, ages, speeds).

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