Line K is tangent to the circle with center (0, 0) at (-3, y) such tha

Question

Line K is tangent to the circle with center (0, 0) at (-3, y) such that its y-intercept is positive. If the radius of the circle is 5, what is the slope of Line K?

A.  -\frac{4}{3}

B.  -\frac{3}{4}

C.  \frac{3}{4}

D.  \frac{1}{2}

E. Cannot be determined

laddaboy · Accepted Answer

Slope of two perpendicular lines is -1.

Distance between the points is 5 , hence solving for y

(-3) ^ 2 + y^2 = 5^2

y = 4

Hence the equation of line is

Since y=mx+c , using the points 0,0 and -3,4 we get m = -4/3. Hence slope of line will be 3/4. Option C

Bunuel · Answer

OFFICIAL EXPLANATION: FROM CRACK VERBAL:

Since the circle is centered at (0, 0), has a radius of 5 and is tangent at (-3, y), using the distance formula we can find the value of y.

5^2 = (-3 – 0)^2 + (y – 0)^2 ---> 25 = 9 + y^2 --> y^2 = 16 --> y = 4

Now to find the slope of line K ideally we will require two points on the line, but we know that the radius and the tangent in a circle are always going to be perpendicular to each other. If two lines are perpendicular, the product of the slopes will always be equal to -1.

Here line K and the radius are perpendicular to each other and we have two points on the radius i.e. (0, 0) and (-3, 4). The slope of the radius will be -4/3. Since line K is perpendicular to the radius, the slope of line K will be ¾.

prashanths · Answer

Radius is given to be 5.

Tangent would meet the circle at a point such that it is perpendicular to the radius drawn from the centre to the point of intersection.

Given that the tangent meets the circle at (-3,y).

Using distance formula (0-(-3))^2 + (0-y)^2 = 5^2
y^2 = 16
y = +/- 4

Slope of radius line= (y2-y1)/(x2-x1) = (0+/-4)/(0-3)
=+/- 4/3

Slope of tangent*Sloe of radius line = -1
Slope of tangent = 3/4 or -3/4

So, it cannot be determined
Option E.

Shrinidhi · Answer

(x−a)^2+(y−b)^2=r^2

(-3-0)^2+(y-0)^2=5^2
9+y^2=25
y^2=25-9=16
y=+4/-4
As Y-intercept in positive,y=4
slope=-4/3

shridhar786 · Answer

since centre of circle (0,0) radius=5
equation of circle  (x-a)^2+(y-b)^2 = r^2  (where a,b centre of circle and r radius)
 x^2+y^2=25 
line k is tangent at (-3,y) so this point lies on circle
now putting values of x and y in equation
9+ y^2 =25
 y^2 =16
y has two values +4 and -4
we will take y=4 ( since given that line k has positive y intersept)
now we can find the slope
points are (-3,4)
slope=tan θ (θ is angle)= \frac{y}{x} = \frac{4}{-3} 
A is the answer

taransaurav · Answer

Given - Point of tangent to the circle with center at O(0,0) is A(-3,y) and the Radius is 5.

So OA^2 = (0 - (-3))^2 + (0 - y)^2 = 5^2 
Gives y=4 (Not -4 since y intercept is positive)

Let slope of OA be m1 = (4-0)/(-3-0) = -4/3

Slope of tangent is m2 = -1/m1 (Property of slopes of perpendicular lines) = 3/4

Answer C

Shishou · Answer

We need to establish 2 baselines here : If the line K is tangent to the circle,It is perpendicular to the radius at the point of tangency. If the y intercept of line K is positive it means Line K exists in Quadrant I and II and maybe Quadrant III. To find y we find the distance between the centre of the circle and the point (-3,y). Which gives us y^2=16. y could be 4/-4 but because line K is tangent to the circle in Quadrant I, y is 4. Now we need to find the slope of the radius which will be the negative reciprocal of line K. Finding the slope of the radius/line with points (0,0) and (-3,4) gives -4/3.The negative reciprocal of this will be 3/4.Thus C

Skywalker18 · Answer

Line K is tangent to the circle with center (0, 0) at (-3, y) such that its y-intercept is positive. If the radius of the circle is 5, what is the slope of Line K?

A.  -\frac{4}{3}

B.  -\frac{3}{4}

C.  \frac{3}{4}

D.  \frac{1}{2}

E. Cannot be determined

Line K is tangent to the circle with center (0, 0) at (-3, y) such that its y-intercept is positive

Since y-intercept is positive--> line rises as it moves towards the right
(-3,y) lies on the circumference of the circle with radius 5
y= 4
x^2+y^2= r^2

Line K is perpendicular to line L(that joins point (-3,4) and center of circle(0,0)
Slope of line L = -4/3

Slope of line K = 3/4 (Product of slope of perpendicular lines is -1)

Answer C

DisciplinedPrep · Answer

Given that, 
 
Radius of the circle = 5
Tangent K meets the circle with center (0, 0) at (-3, y)
 According to Tangent Theorem, the radius from the center of the circle to the point of tangency is perpendicular to the tangent line.

Therefore, we can solve for y, using the Pythagoras theorem.
 -3^{2} +  y^{2}  =  5^{2} 
 y^{2}  = 16
y = 4 
Note: Since the question specifives the y intercept is positive, we can ignore the negative value of y, i.e. y = -4

Now using the slope equation of a straight line, y = mx + c, where m is slope and c is the y-intercept, we can find the equation of the radius 
The slope of the radius is  \frac{-4}{3}

The product of the slopes of two perpendicular lines is -1 
Therefore, (slope of radius) x (slope of line k) = -1

Slope of line k =  \frac{3}{4}

The correct answer is option C.  \frac{3}{4}

saukrit · Answer

The correct answer is C (3/4)

How?

Well, the tangent touches the circle at one point and is perpendicular to the radius. That point is given as (-3,y) and we also know that radius is 5 units.

Now for the radius to be 5 units . Let us consider the radius to be a line with 2 points A, B. A is the origin (0,0) and B is (-3,y). And distance between A and B is 5

Therefore, \sqrt{(x2-x1)^2 +(y2-y1)^2} =5 
 3^2 +y^2=5^2 
 y^2=16 
 y=4

Slope of line AB =  \frac{(y2-y1)}{(x2-x1)}  =  \frac{(4)}{(-3)}  =  \frac{-4}{3}

Radius and tangent are perpendiculars

Product of slope of 2 perpendicular lines = m1*m2=-1

\frac{-4}{3} * (Slope of Tangent) =-1 
Hence. The slope of Tangent = \frac{3}{4}

RajatVerma1392 · Answer

Hi,

As given y>0, and tangent touches at (-3,y), and the radius = 5.
We can use the distance formula between points to find y.
 \sqrt{{(-3-0)^2} + {(y-0)^2}}  =  \sqrt{{5^2}}

This will give us y= +4 or -4 , since we know y> 0, so y= +4.

Now, the point is (-3,4). We can use the line equation between points:

(y-0) =  \frac{(4-0)}{(-3-0)}  * (x-0)
y = (-4/3) x

As per the property of circle, the tangent should touch at 90-degree angle, so the slope formula is => m1 * m2 = -1 
using the formula we get :
(-4/3) * m2 = -1 
m2 = (3/4)

Ans = 3/4

Please hit Kudos if you like the solution.

Gilmour92 · Answer

Line K is tangent to the circle at the point (-3,y). Let’s call this point A.

The centre of the circle is C (0,0).

Let’s drop a perpendicular from A to the x-axis. The co-ordinate of the same is (-3,0). We’ll call this point B.

Joining the three points, we get a right angled triangle right angled at B. The sides are: AB = y, BC = 3, AC = 5 (radius)

Using Pythagoras theorem, we get y = 4. Hence, the point of tangency A is (-3,4).

The slope of the line AC is: (0-4)/(0+3) = -4/3

As line K is perpendicular to AC (property of tangency), the slope of K is the negative reciprocal, ie. 3/4.

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XyLan · Answer

Since y-intercept is positive and the intersection point lies on the perimeter of the circle,
 (-3)^2 + y^2 = R^2  - where R = 5

(-3)^2 + y^2 = 25

Therefore, y = +4 as y-intercept is positive
.
Moreover, The  tangent-Line1  and  Line2   formed by joining intersection-point A(-3, 4) and center(0,0) ] are perpendicular to each other.
Thus, the product of their slopes is -1. -

Slope of  Line2  =  Y2 - Y1/ X2 - X1  
 4 - 0 / (-3) - 0  =  -4/3

Hence, slope of  tangent-Line1  =  3/4

MahmoudFawzy · Answer

Knowing that y intersect is (+ve) means that the slope is positive, so A & B are out.

The point of tangency between line K and the circle make a triangle with the origin and the x-intersect point (-3,0).
if the radius is 5, then the point of tangency is (-3,4) following a Pythagoras triple.

if the slope of the radius  perpendicular  to the tangent line k is 4/-3, then the slope of the tangent k is 3/4 (negative the inverse).  C

Sayon · Answer

Given: 
Circle with center at (0, 0) 
The radius of the circle: 5

From the above data,
The equation of the Circle formed is:  (x-0)^2 + (y-0)^2 = 5^2 => x^2 + y^2 = 25

Given: 
Line K is a tangent to the above circle at (-3,y) such that its y-intercept is positive.

To find the value of y, we put the coordinate (-3,y) in the equation of our circle:
 x^2 + y^2 = 25 => (-3)^2+y^2 = 25  => y = +4 (or) -4
Since the y-intercept is positive, by looking at the figure formed we understand that y = 4
Thus, the point at which the Tangent intersects the circle is (-3,4). (Fig 2)

Finding the slope of the tangent:

The radius from the center of the circle to the point of tangency is perpendicular to the tangent line.  
Thus, if we draw a radius to like K they will be perpendicular to each other.

The product of the “slopes” of two perpendicular lines is -1   
(Slope of the radius to the tangent)*(Slope of line K) = -1
=>  \frac{(0-4)}{(0+3)} * (slope of line K) = -1
=> \frac{-4}{3} * (slope of line K) = -1
=> The slope of line K = \frac{3}{4}

Answer: C

GMATinsight · Answer

https://www.youtube.com/watch?v=aZkJWALQfCQ

Please find attached the video solution.

MayankSingh · Answer

radius=5
5^2=3^2+y^2
y=+-4
Since Y intercept positive, y=4
From Image, tan Ѳ= tan(90-y)= coty=3/4
Ans C

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Line K is tangent to the circle with center (0, 0) at (-3, y) such tha

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Line K is tangent to the circle with center (0, 0) at (-3, y) such tha

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