Tag: construction of triangles - i

Questions Related to construction of triangles - i

The perimeter of a triangle is $45\ cm$. Length of the second side is twice the length of first side. The third side is $5$ more than the first side. Find the length of each sides and construct the triangle made by these three sides.

  1. $11,19,15$

  2. $10,20,15$

  3. $10,16,19$

  4. $13,15,17$


Correct Option: B
Explanation:

Let the length of first side $=x$

Length of second side $=2x$
Length of third side $=x+5$
Perimeter $=45cm$
$x+2x+x+5=45\ 4x=45-5\ 4x=40\ x=10$
So the sides are
$x=10$
$2x=2\times 10=20\ x+5=10+5=15$
Option $B$ is correct.

Construct a triangle $ABC$ in which $AB = 5 cm$ and $BC = 4.6 cm$ and $AC = 3.7 cm$
Steps for the construction is given in jumbled form.Choose the appropriate sequence for the above
1) With radius as $5\ cm$ from $C$, cut an arc.
2)They arcs will intersect at point $A$. Join $AB$ and $AC$. $ABC$ is the required triangle.
3)Draw a line segment $BC = 4\ cm.$
4)With radius as $3$ cm from $B$, cut the arc. 

  1. $1,4,3,2$

  2. $4,3,2,1$

  3. $3,1,4,2$

  4. $4,1,3,2$


Correct Option: C
Explanation:

Correct sequence is:

1. Draw a line segment $AB=4$ cm.
2. With radius $5$ cm from $C$ , cut an arc.
3. With radius $3$ cm from $B$ , cut an arc.
4. The arc will intersect at point $A$, Join $AB$ and $AC$ .$ABC$ is required triangle.
So correct sequence is $3,1,4,2$
So option $C$ is correct.

Construct an isosceles $\triangle  XYZ,$ where $YZ=5$ units and $\angle XYZ=35^{o}$. Also, find the measure of $\angle YXZ$.

  1. $35^{o}$

  2. $70^{o}$

  3. $110^{o}$

  4. $140^{o}$


Correct Option: C
Explanation:

$YZ=5$ CM $,\angle XYZ=35^{\circ}$

As the triangle is isosceles therefore $\angle XZY=50^{\circ}$
Steps of construction:
1. Draw a line segment $XY=5$ cm.
2. At $Y$ draw an angle of $35^{\circ}$ and extend the arm.
3. At $Z$ draw an angle of $35^{\circ}$ and extend the ray such that it intersect the previous ray at $X$
4. Join $Y$ to $X$ and $Z$ to $X$
Now measure $\angle YXZ$
$\angle YXZ=110^{\circ}$

Construct an isosceles $\triangle  ABC,$ where base $AB=7\ cm$ and $\angle ABC=50^{o}$. Also, find the measure of $\angle ACB$.

  1. $50^{0}$

  2. $80^{o}$

  3. $100^{o}$

  4. $120^{o}$


Correct Option: B
Explanation:

$AB=7$ cm $,\angle ABC=50^{\circ}$

As the triangle is isosceles therefore $\angle CAB=50^{\circ}$
Steps of construction:
1. Draw a line segment $AB=7$ cm.
2. At $A$ draw an angle of $50^{\circ}$ and extend the arm.
3. At $B$ draw an angle of $50^{\circ}$ and extend the ray such that it intersect the previous ray at $C$
4. Join $A$ to $C$ and $B$ to $C$
Now measure $\angle ACB$
$\angle ACB=80^{\circ}$

For construction of a $\triangle PQR$, where $\displaystyle QR=6\ cm, PR=10\ cm$ and $\angle Q=90^{\circ}$, its steps for construction is given below in jumbled form. Identify the fourth step from the following.

1. At point $ Q $, draw an angle of $ {90}^{\circ} $.
2. From $ R $ cut an arc of length $ PR = 10.0 \ cm $ using a compass .
3. Name the point of intersection of the arm of the angle $ {90}^{\circ} $ and the arc drawn in step 3, as $ P $.
4. Join $P $ to $ Q $ . $ PQR $ is the required triangle. 
5. Draw the base side $ QR = 6\  cm $.

  1. $5$

  2. $1$

  3. $2$

  4. $3$

  5. $4$


Correct Option: D
Explanation:

Step 1. Draw a line $QR=6\ \ cm$

Step 2. At point $Q$ ,draw an angle of $90^{\circ}$
Step 3. From $R$ cut an arc $PR=10\ \ cm$ using compass.
Step 4. Name the point of intersection of the arm of angle $90^{\circ}$ and the arc in step $3$ , as $P$
Step 5. Join $P$ to $Q$. $PQR$ is required triangle.
So the fourth step is $3$
Option $D$ is correct.

State the following statement is True or False
In a right angle triangle $ABC$ such as $AC=5 cm ,BC=2 cm$ , $\angle B=90^o$
Then the length of $AB$ after construction is $7$cm

  1. True

  2. False


Correct Option: B
Explanation:

In the given triangle $\Delta ABC$:


$AC=5$ and $BC=2$.

So by the property of triangle(sum of two sides are always greater than the third side):

$AB<(AC+BC)\implies AB<7$.

But in the given question it is given that $AB=7$, which is not possible.
So given statement is incorrect.

For construction of a $\triangle PQR$, where $\displaystyle QR=6\ cm, PR=10\ cm$ and $\angle Q=90^{\circ}$, its steps for construction is given below in jumbled form. Identify the second step from the following.

1. At point $ Q $, draw an angle of $ {90}^{\circ} $.
2. From $ R $ cut an arc of length $ PR = 10.0 \ cm $ using a compass.
3. Name the point of intersection of the arm of the angle $ {90}^{\circ} $ and the arc drawn in step 3, as $ P $.
4. Join $P $ to $ Q $ . $ PQR $ is the required triangle. 
5. Draw the base side $ QR = 6\  cm $.

  1. $2$

  2. $1$

  3. $4$

  4. $5$

  5. $3$


Correct Option: B
Explanation:

Step 1. Draw a line $QR=6\ \ cm$

Step 2. At point $Q$ ,draw an angle of $90^{\circ}$
Step 3. From $R$ cut an arc $PR=10\ \ cm$ using compass.
Step 4. Name the point of intersection of the arm of angle $90^{\circ}$ and the arc in step $3$ , as $P$
Step 5. Join $P$ to $Q$. $PQR$ is required triangle.
So the second step is $1$
Option $B$ is correct.

For construction of a $\triangle PQR$, when $\displaystyle QR=6\ cm, PR=10\ cm$ and $\angle Q=90^{\circ}$, its steps for construction is given below in jumbled form. Identify the fifth step from the following.

1. At point $ Q $, draw an angle of $ {90}^{\circ} $.
2. From $ R $ cut an arc of length $ PR = 10.0 \ cm $ using a compass.
3. Name the point of intersection of the arm of the angle $ {90}^{\circ} $ and the arc drawn in step 3, as $ P $.
4. Join $P $ to $ Q $ . $ PQR $ is the required triangle. 
5. Draw the base side $ QR = 6\  cm $.

  1. $2$

  2. $3$

  3. $1$

  4. $5$

  5. $4$


Correct Option: E
Explanation:

Step 1. Draw a line $QR=6\ \ cm$

Step 2. At point $Q$ ,draw an angle of $90^{\circ}$
Step 3. From $R$ cut an arc $PR=10\ \ cm$ using compass.
Step 4. Name the point of intersection of the arm of angle $90^{\circ}$ and the arc in step $3$ , as $P$
Step 5. Join $P$ to $Q$. $PQR$ is required triangle.
So the fifth step is $4$
Option $E$ is correct.

For construction of a $\triangle PQR$, where $\displaystyle QR=6\ cm, PR=10\ cm$ and $\angle Q=90^{\circ}$, its steps for construction is given below in jumbled form. Identify the first step from the following.

1. At point $ Q $, draw an angle of $ {90}^{\circ} $.
2. From $ R $ cut an arc of length $ PR = 10.0 \ cm $ using a compass .
3. Name the point of intersection of the arm of the angle $ {90}^{\circ} $ and the arc drawn in step 3, as $ P $.
4. Join $P $ to $ Q $ . $ PQR $ is the required triangle. 
5. Draw the base side $ QR = 6\  cm $.

  1. $2$

  2. $1$

  3. $3$

  4. $5$

  5. $4$


Correct Option: D
Explanation:

Step 1. Draw a line $QR=6\ \ cm$

Step 2. At point $Q$ ,draw an angle of $90^{\circ}$
Step 3. From $R$ cut an arc $PR=10\ \ cm$ using compass.
Step 4. Name the point of intersection of the arm of angle $90^{\circ}$ and the arc in step $3$ , as $P$
Step 5. Join $P$ to $Q$. $PQR$ is required triangle.
So the first step is $5$
Option $D$ is correct.

Construct a triangle $ABC$, in which $AB = 5.5 cm, AC = 6.5 cm$ and $\angle BAC = 70^{\circ}$.
Steps for its construction is given in a jumbled form.Identify its correct sequence.
1) At $A$, construct a line segment $AE$, sufficiently large, such that $\angle BAC$ at $70^\circ$, use protractor to measure $70^\circ$
2) Draw a line segment which is sufficiently long using ruler.
3) With $A$ as centre and radius $6.5cm$, draw the line cutting $AE$ at C, join $BC$, then $ABC$ is the required triangle.
4) Locate points $A$ and $B$ on it such that $AB = 5.5cm$.

  1. $2,4,1,3$

  2. $2,1,4,3$

  3. $1,2,4,3$

  4. $4,2,1,3$


Correct Option: A
Explanation:

Below are the correct steps.

i) Draw a line segment which is sufficiently long using ruler.
ii) Locate points $A$ and $B$ on it such that $AB=5.5 \ cm$
iii) At $A$ construct a line segment $AE$ , sufficiently large, such that $\angle BAC=70^\circ$, use protractor to measure
iv) With $A$ as centre and radius $6.5 \ cm$ draw the line cutting $AE$ at $C$, join $BC$ then $ABC$ is the required triangle.

So, the correct sequence of given steps is $2,4,1,3$.