Question
To conduct Sports Day activities, in your rectangular-shaped school ground $ABCD,$ lines have been drawn with chalk powder at a distance of $1m$ each. $100$ flower pots have been placed at a distance of $1m$ from each other along $AD,$ as shown in Figure. Niharika runs $\frac{1}{4}$th the distance $AD$ on the $2nd$ line and posts a green flag. Preet runs $\frac{1}{5}$th the distance $AD$ on the eighth line and posts a red flag. What is the distance between both the flags$?$ If Rashmi has to post a blue flag exactly halfway between the line segment joining the two flags, where should she post her flag$?$

Answer

It can be observed that Niharika posted the green flag at $\frac{1}{4}$th of the distance $AD$ i.e., $\frac{1}{4} \times 100 = 25m$ from the starting point of $2^{nd}$ line. Therefore, the coordinates of this point $G$ is $(2, 25)$
Similarly, Preet posted a red flag at $\frac{1}{5}$th of the distance $AD$ i.e., $\frac{1}{5} \times 100 = 20m$ from the starting point of $8^{th}$ line. Therefore, the coordinates of this point $R$ are $(8, 20)$
Now we have the positions of posts by Preet and Niharika
According to distance formula, the distance between points $A(x_1, y_1)$ and $B(x_2, y_2)$ is given by
$D=\sqrt{\left(x_{2}-x_{1}\right)^{2}+\left(y_{2}-y_{1}\right)^{2}}$
Distance between these flags by using distance formula,
$D=\sqrt{\left(8-2_{}\right)^{2}+\left(25_{}-{20}\right)^{2}}$
$=\sqrt{36+25} \mathrm {m}$
$=\sqrt{61} \mathrm{m}$
The point at which Rashmi should post her blue flag is the mid-point of the line joining these points. Let this point be $A (X,Y)$
Now by midpoint formula,
$(X, Y)=\left(\frac{x_{1}+x_{2}}{2}, \frac{y_{1}+y_{2}}{2}\right)$
$X=\left(\frac{2+8}{2}\right)=5$
$Y=\left(\frac{25+20}{2}\right)=22.5$
Hence,$ A (X,Y) = (5, 22.5)$
Therefore, Rashmi should post her blue flag at $22.5m$ on the $5^{th}$ line.

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