Geometry Questions

Multiple choice maths introduction to three dimensional geometry coordinate axes and coordinate planes in 3d space coordinates in 3d introduction to 3d geometry

If G is the centroid of $\triangle ABC$ and BC = 3, CA = 4, AB = 5 then BG =

  1. $\dfrac { \sqrt { 73 } }{ 3 } $
  2. $\dfrac { \sqrt { 13 } }{ 3 } $
  3. $\dfrac { \sqrt { 52 } }{ 3 } $
  4. $\dfrac { \sqrt { 26 } }{ 3 } $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The triangle with sides 3, 4, 5 is a right triangle. Using Apollonius theorem or coordinate geometry, the length of the median to side AB (c=5) is m_c = 1/2 * sqrt(2a^2 + 2b^2 - c^2) = 1/2 * sqrt(2*16 + 2*9 - 25) = 1/2 * sqrt(7) = sqrt(7)/2. The centroid G divides the median in a 2:1 ratio, so BG = 2/3 * m_c = 2/3 * sqrt(7)/2 = sqrt(7)/3. However, checking the options, sqrt(52)/3 is 2*sqrt(13)/3. Let's re-verify: median to AB is 1/2 * sqrt(2*16 + 2*9 - 25) = sqrt(7)/2. The distance BG is 2/3 of the median. None match perfectly. Re-evaluating: maybe median to BC? m_a = 1/2 * sqrt(2*16 + 2*25 - 9) = 1/2 * sqrt(32+50-9) = sqrt(73)/2. BG = 2/3 * sqrt(73)/2 = sqrt(73)/3. Option A is sqrt(73)/3. Wait, the question asks for BG, which is the segment from vertex B to centroid G. This is 2/3 of the median from B to AC. Median m_b = 1/2 * sqrt(2*a^2 + 2*c^2 - b^2) = 1/2 * sqrt(2*9 + 2*25 - 16) = 1/2 * sqrt(18+50-16) = 1/2 * sqrt(52) = sqrt(52)/2. BG = 2/3 * sqrt(52)/2 = sqrt(52)/3.

Multiple choice maths properties of parallel lines and their transversal how to check for similarity in triangles? criteria for similarity of triangles criteria for triangle similarity

The perimeters of two similar triangles ABC and LMN are 60 cm and 48 cm respectively If LM=8 cm, the length of AB is

  1. $10\ cm$
  2. $8\ cm$
  3. $6\ cm$
  4. $4\ cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If two triangles are similar then the ratio of their perimeter is equal to the ratio of their corresponding sides.

$\therefore \dfrac{perimeter\ ABC}{perimeter\ LMN}=\dfrac{AB}{LM}$
$\Rightarrow \dfrac{60}{48}=\dfrac{AB}{8}$
$\Rightarrow AB=\dfrac{60\times 8}{48}=10 cm$

Multiple choice maths properties of parallel lines and their transversal how to check for similarity in triangles? criteria for similarity of triangles criteria for triangle similarity

The perimeters of two similar triangles ABC and PQR are 60 cm and 48 cm respectively If PQ=8 cm length of AB is

  1. $10\ cm$
  2. $8\ cm$
  3. $6\ cm$
  4. $4\ cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$P _1=AB+BC+AC=60  cm$

$P _2=PQ+QR+RP=48  cm$
PQ=8 cm
$\dfrac{P _1}{P _2}=\dfrac{AB}{PQ}$
$\Rightarrow \dfrac{60}{48}=\dfrac{AB}{8}$
$\Rightarrow AB=\dfrac{60\times 8}{48}=10 cm$

Multiple choice maths measuring time time in 24 hour clock time difference time

A clock has numbers $1$ to $12$. If a clock has a shape of a circle, then the degree measure made by an arc between any two consecutive numbers of the clock is

  1. $60$
  2. $30$
  3. $45$
  4. $90$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$12\rightarrow \frac { 360 }{ 12 } 30$

Multiple choice maths bearing and drawings mapping mapping space around us changing scale

Triangle $ABC$ is such that $AB=3cm, BC=2cm$ and $CA=2.5cm$. Triangle $DEF$ is similar to $\triangle ABC$. If $EF=4cm$, then the perimeter of $\triangle DEF$ is:

  1. $7.5cm$
  2. $15cm$
  3. $22.5cm$
  4. $30cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given: $AB = 3 cm$, $BC = 2 cm$ and $CA = 2.5 cm$ and $EF = 4 cm$ 

Also, $\triangle ABC \sim \triangle DEF$

Thus, $\dfrac{AB}{DE} = \dfrac{BC}{EF} = \dfrac{AC}{DF}$

$\dfrac{3}{DE} = \dfrac{2}{4} = \dfrac{2.5}{DF}$

Hence, $DE = 6 cm$ and $DF = 5 cm$

Perimeter of $\Delta$ DEF = $DE + EF + EF$

Perimeter of $\Delta$ DEF = $4 + 5 + 6$

Perimeter of $\Delta$ DEF = $15$ cm

Multiple choice maths bearing and drawings mapping mapping space around us changing scale

The areas of two similar triangles are $48{cm}^{2}$ and $75{cm}^{2}$ respectively. If the altitude of the first triangle be $3.6cm$, find the corresponding altitude of the other.

  1. $4cm$
  2. $4.5cm$
  3. $5cm$
  4. $5.5cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ar. ($\triangle _{1}$) = $48 cm^2$
Ar. ($\triangle _{2}$) = $75 cm^2$
$a _{1} = 3.6 cm$
For similar triangles the ratio of areas is equal to the ratio of square of their altitudes.
Thus, $\frac{A(\triangle _{1})}{A(\triangle _{2})} = \frac{(a _1)^2}{(a _2)^2}$
$\frac{48}{75} = \frac{(3.6)^2}{(a _2)^2}$
$(a _2)^2 = \frac{12.96 \times 75}{48}$
$(a _2)^2 = 20.25$
$a _2 = 4.5$cm

Multiple choice maths bearing and drawings mapping mapping space around us changing scale

$\triangle ABC$ and $\triangle PQR$ are similar triangle such that area $(\triangle ABC)=49{cm}^{2}$ and Area $(\triangle PQR)=25{cm}^{2}$. If $AB=5.6cm$, find the length of $PQ$.

  1. $4cm$
  2. $5cm$
  3. $5.6cm$
  4. $7cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ar. ($\triangle ABC$) = $49 cm^2$
Ar. ($\triangle PQR$) = $25 cm^2$
$AB = 5.6 cm$
For similar triangles the ratio of areas is equal to the ratio of square of its sides.
Thus, $\dfrac{A(\triangle ABC)}{A(\triangle PQR)} = \dfrac{AB^2}{PQ^2}$
$\dfrac{49}{25} = \dfrac{(5.6)^2}{PQ^2}$
$PQ^2 = \dfrac{31.36 \times 25}{49}$
$PQ^2 = 16$
$PQ = 4$cm

Multiple choice maths bearing and drawings mapping mapping space around us changing scale

The perimeter of two similar triangles $ABC$ and $PQR$ are $36\ cm$ and $24\ cm$ respectively. If $PQ = 10\ cm$ then the length of $AB$ is

  1. $18\ cm$
  2. $12\ cm$
  3. $15\ cm$
  4. $30\ cm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\triangle ABC = \triangle PQR$, then
$\dfrac {\text {Perimeter of}\triangle ABC}{\text {Perimeter of}\triangle PQR} = \dfrac {AB}{PQ} = \dfrac {BC}{QR} = \dfrac {AC}{PR}$
$\dfrac {36}{24} = \dfrac {AB}{10}; AB = \dfrac {36}{24}\times 10 = 15\ cm$.

Multiple choice mathematics and statistics hyperbola auxiliary circle auxiliary circle, director circle director circle and auxiliary circle of a hyperbola

If the chords of contact of tangents drawn from $P$ to the hyperbola $x^2 - y^2 = a^2$ and its auxiliary circle are at right angle, then $P$ lies on :

  1. $x^2 - y^2 = 3a^2$
  2. $x^2 - y^2 = 2a^2$
  3. $x^2 - y^2 = 0$
  4. $x^2 - y^2 = 1$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let $P$ be $(h,k)$
Now Chord of contact of tangent from $P$ to the hyperbola $x^2-y^2=a^2$ is,
$T =0\Rightarrow hx -ky = a^2$ (i)
And director circle of given hyperbola is, $x^2+y^2=a^2$
Thus equation of chord of contact to this circle from P is, $hx+ky = a^2$ (ii)
Now given line (i) and (ii) are perpendicular,
$\Rightarrow \cfrac{h}{k}\times \cfrac{-h}{k}=-1\Rightarrow h^2=k^2$
Hence locus of $P$ is given by, $x^2-y^2=0$ 

Multiple choice maths surface area and volume of cube and cuboid length of the diagonal diagonal of cube and cuboid surface area of cubes and cuboids

A person wishes to fit three rods together in the shape of a right-angled triangle so that the hypotenuse is to be $4:cm$ longer than the base and $8:cm$ longer than the altitude. The lengths of the rods are:

  1. $3\:cm$, $4\:cm$, $5\:cm$
  2. $1.5\:cm$, $2\:cm$, $2.5\:cm$
  3. $6\:cm$, $8\:cm$, $10\:cm$
  4. $12\:cm$, $16\:cm$, $20\:cm$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let the altitude$=x:cm$
$\therefore$ The Base$=(x+4):cm$
and the Hypotenuse$=(x+8):cm$

Using Pythtegores Theorem
$(x+8)^2=(x+4)^2+x^2$
$x^2-8x-48=0$
$(x-12)(x+4)=0$
$x=12$
$\therefore$ The sides are $12:cm$, $16:cm$, $20:cm$ 

Multiple choice maths surface area and volume of cube and cuboid length of the diagonal diagonal of cube and cuboid surface area of cubes and cuboids

Hypotenuse of a right triangle is $25cm$ and out of the remaining two sides, one is longer than the other by $5cm$. Find the lengths of the other two sides.

  1. $10$cm and $20$ cm
  2. $15$cm and $20$ cm
  3. $25$cm and $20$ cm
  4. $5$cm and $20$ cm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let one side be $xcm$. Then the other side will be $(x+5)cm$. Therefore, from Pythagoras theorem
${x}^{2}+{(x+5)}^{2}={25}^{2}$
$\Rightarrow { x }^{ 2 }+{ x }^{ 2 }+10x+25=625$
$\Rightarrow { x }^{ 2 }+5x-300=0\quad \quad \Rightarrow { x }^{ 2 }+20x-15x-300=0$
$\Rightarrow x(x+20)-15(x+20)=0$
$\Rightarrow (x-15)(x+20)=0\quad \Rightarrow \quad x=15\quad or\quad x=-20$
Rejecting $x=-20$, we have length of one side $=15cm$ and that of the other side $=(15+5)cm=20cm$

Multiple choice maths surface area and volume of cube and cuboid length of the diagonal diagonal of cube and cuboid surface area of cubes and cuboids

The length of the hypotenuse of a right angled $\Delta$ whose two legs measure $12 \ cm$ and $0.35 \ m$ is:

  1. $37 \ cm$
  2. $3.72 \ cm$
  3. $0.372 \ cm$
  4. $37 \ m$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$0.35 \ m = 0.35 \times 100 \ cm = 35 \ cm.$
We have,
$(hypotenuse)^2\, =\, (side)^2\, +\, (side)^2$
$=\, (12)^2\, +\, (35)^2$
$= 144 + 1225$
$= 1369$
Hypotenuse $=\sqrt{1369} = 37 \ cm.$

Multiple choice maths circle measures area of a sector of a circle sector and arc of a circle area of sectors and segments

If the area and arc length of the sector of a circle are 60 $cm^2$ and 20 cm respectively, then the diameter of the circle is 

  1. 6 cm

  2. 12 cm

  3. 24 cm

  4. 36 cm

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Arc length of the Circle  : Area of the Sector = Perimeter of the Circle :Area of the Circle

Let the radius of the circle be 'r'.

 

Hence, $20 : 60$=$ 2\pi r : \pi r^2$

$ 1:3 = 2: r$

$ r= 6 $ (Product of Means = Product of Extremes)

Therefore, $Diameter = 2r = 12cm$