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Ananya thinks of a positive integer. Adding the number to its reciprocal gives her . Which integer did she think of?

Class 10Quadratic EquationsAlgebra — Quadratics
  • A50
  • B14
  • C
  • D7

Step-by-Step Solution

Let the number be . Multiply by → , so or . Both are positive, but only 7 is an INTEGER, so that is Ananya's number is the other root, correctly rejected here by the word "integer" rather than by sign. 50 and 14 are the numerator and denominator of the working, not roots.
Answer: D) 7

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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