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At present Asha’s age (in years) is 2 more than the square of her daughter Nisha’s age. When Nisha grows to her mother’s present age, Asha’s age would be one year less than 10 times - Mathematics

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Sum

At present Asha’s age (in years) is 2 more than the square of her daughter Nisha’s age. When Nisha grows to her mother’s present age, Asha’s age would be one year less than 10 times the present age of Nisha. Find the present ages of both Asha and Nisha.

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Solution

Let Nisha’s present age be x year.
Then, Asha’s present age = x2 + 2  .....[By given condition]
Now, when Nisha grows to her mother’s present age

i.e., After [(x2 + 2) – x] yr.

Then, Asha’s age also increased by [(x2 + 2) – x] year.

Again by given condition,

Age of Asha = One years less than 10 times the present age of Nisha

`(x^2 + 2) + {(x^2 + 2) - x} = 10x - 1`

⇒ `2x^2 - x + 4 = 10x - 1`

⇒ `2x^2 - 11x + 5` = 0

⇒ `2x^2 - 10x - x + 5` = 0

⇒ `2x(x - 5) - 1(x - 5)` = 0

⇒ `(x - 5)(2x - 1)` = 0

∴ `x = 5`

[Here, `x = 1/2` cannot be possible, because at `x = 1/2`, Asha's age is `2/4` year whuch is not possible]

Hence, required age of Nisha = 5 year

And required age of Asha = `x^2 + 2 = (5)^2 = 25 + 2` = 27 year 

Concept: Nature of Roots
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APPEARS IN

NCERT Mathematics Exemplar Class 10
Chapter 4 Quadatric Euation
Exercise 4.4 | Q 6 | Page 42
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