# NIELIT 2019 Feb Scientist C - Section D: 13

122 views

Two persons start walking on a road that diverge at an angle of $120^{\circ}$. If they walk at the rate of $3$km/h and $2$km/h respectively.

Find the distance between them after $4$hrs.

1. $4\sqrt{19}$ km
2. $5$ km
3. $7$ km
4. $8\sqrt{19}$ km

recategorized

Ans is option (A)

Using the cosine rule of triangle trigonometry ,

$cosC=\frac{a^{2}+b^{2}-c^{2}}{2ab}$

$\Rightarrow$   $cos120^{\circ}=\frac{64+144-c^{2}}{2\times8\times12}$

$\Rightarrow$  $c^{2}=304$   $\Rightarrow$  $c=4\sqrt{19}km$
238 points 2 2 4

## Related questions

1
67 views
On a scale of a map, $0.6$ cm represents $6.6$ km. If the distance between two points on the map is $80.5$ cm, the actual distance between these points is: $9$ km $72.5$ km $190.75$ km $885.5$ km
2
118 views
The minute hand is $10$ cm long. Find the area of the face of the clock described by the minute hand between $9$ a.m and $9:35$ a.m. ${183.3\ cm^{2}}$ ${366.6\ cm^{2}}$ ${244.4\ cm^{2}}$ ${188.39\ cm^{2}}$
Determine $a+b$ such that the following system of equations: $2x-(a-4)y=2b+1 \text{ and }4x-(a-1)y=5b-1$ infinite solutions. $11$ $9$ $10$ $8$
The line $x+y=4$ divides the line joining $\text{(-1,1) & (5,7)}$ in the ratio $\lambda : 1$ then the value of $\lambda$ is: $2$ $3$ $\dfrac{1}{2}$ $1$