CBSE 2025 · Region 6 · Set 1 · Q32 · 5 marks
There is a circular park of diameter $\displaystyle 65$ m as shown in the following figure, where AB is a diameter.
An entry gate is to be constructed at a point P on the boundary of the park such that distance of P from A is $\displaystyle 35$ m more than the distance of P from B . Find distance of point P from A and B respectively.Find the smallest value of p for which the quadratic equation $\displaystyle x^{2}-2(\mathrm{p}+1) x+\mathrm{p}^{2}=0$ has real roots. Hence, find the roots of the equation so obtained.
There is a circular park of diameter $\displaystyle 65$ m as shown in the following figure, where AB is a diameter.
An entry gate is to be constructed at a point P on the boundary of the park such that distance of P from A is $\displaystyle 35$ m more than the distance of P from B . Find distance of point P from A and B respectively.
Find the smallest value of p for which the quadratic equation $\displaystyle x^{2}-2(\mathrm{p}+1) x+\mathrm{p}^{2}=0$ has real roots. Hence, find the roots of the equation so obtained.
Marking-scheme solution
Let distance of gate at P from point B is \(\displaystyle x\) m
Then distance of gate at P from point A is \(\displaystyle (35+x) \mathrm{m}\)
In right \(\displaystyle \Delta \mathrm{APB}\)
\[\begin{aligned}
& (x+35)^{2}+x^{2}=(65)^{2} \\
& x^{2}+35 x-1500=0 \\
& (x+60)(x-25)=0 \\
& x=25
\end{aligned}
\]
Hence, \(\displaystyle x+35=60\)
Distance of P from A = $\displaystyle 60$ m
Distance of P from B = $\displaystyle 25$ m
OR
For real roots, \(\displaystyle \mathrm{D} \geq 0\)
\[\begin{aligned}
{[-2(\mathrm{p}+1)]^{2}-4 \mathrm{p}^{2} } & \geq 0 \\
\Rightarrow \mathrm{p} & \geq-\frac{1}{2}
\end{aligned}
\]
∴ smallest value of \(\displaystyle \mathrm{p}=-\frac{1}{2}\)
At \(\displaystyle \mathrm{p}=-\frac{1}{2}\) given equation becomes
\[x^{2}-2\left(\frac{-1}{2}+1\right) x+\left(\frac{-1}{2}\right)^{2}=0
\]
\(\displaystyle x^{2}-x+\frac{1}{4}=0\) or \(\displaystyle 4 x^{2}-4 x+1=0\)
\[(2 x-1)(2 x-1)=0
\]
∴ roots are \(\displaystyle \frac{1}{2}, \frac{1}{2}\)CirclesTangent to a CircleApplylong_answerhard
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CBSE Class 10 Mathematics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.