Tag: mapping space around us

Questions Related to mapping space around us

A triangle LMN has been reduced by scale factor 0.8 to the triangle L' M' N'. Calculate the length of LM, if L' M'= 5.4 cm.

  1. 6.75 cm

  2. 5.75 cm

  3. 6.25 cm

  4. none of the above


Correct Option: A
Explanation:

$\triangle LMN$ is reduced to $\triangle L'M'N'$,
Thus, $\dfrac{L'M'}{LM} = 0.8$
$\Rightarrow \dfrac{5.4}{LM} = 0.8$
$\Rightarrow LM = \dfrac{5.4}{0.8}$
$\Rightarrow LM = 6.75$ cm 

A triangle LMN has been reduced by scale factor 0.8 to the triangle L' M' N'. Calculate the length of M' N'. if MN= 8 cm.

  1. 6.4 cm

  2. 4.4 cm

  3. 5.4 cm

  4. none of the above


Correct Option: A
Explanation:

$\triangle LMN$ is reduced to $\triangle L'M'N'$,
Thus, $\dfrac{M'N'}{MN} = 0.8$
$\Rightarrow \dfrac{M'N'}{8} = 0.8$
$\Rightarrow M'N' = 0.8 \times 8$
$\Rightarrow M'N' = 6.4 $ cm 

A triangle ABC is enlarged, about the point O as centre of enlargement, and the scale factor is 3. Find BC. if B'C'= 15 cm.

  1. 6 cm

  2. 5 cm

  3. 7 cm

  4. none of the above


Correct Option: B
Explanation:

$\triangle ABC$ is enlarged to $\triangle A'B'C'$,
Thus, $\dfrac{B'C'}{BC} = 3$
$\Rightarrow \dfrac{B'C'}{BC} = 3$
$\Rightarrow BC = \dfrac{15}{3}$
$\Rightarrow BC = 5$ cm 

A has a pair of triangles with corresponding sides proportional, and B has a pair of pentagons with corresponding sides proportional.
$S _1 \equiv $ 
A's triangles must be similar
$S _2 \equiv $ B's pentagons must be similar 
Which of the following statement is correct ? 

  1. $S _1$ is true, but $S _2$ is not true.

  2. $S _2$ is true, but $S _1$ is not true.

  3. Both $S _1$ and $S _2$ are true

  4. Neither $S _1$ and $S _2$ are true


Correct Option: A
Explanation:

For similarity of triangles we have SSS criteria. So $S _1$ is true. 
But for polygons to be similar, the corresponding sides must be in equal ratio as well as the corresponding angles must be congruent.

Since, there is nothing mentioned about the angles of the pentagons, so $S _2$ is false.

A triangle ABC is enlarged, about the point O as centre of enlargement, and the scale factor is 3. Find A'B', if AB = 4cm.

  1. 12 cm

  2. 14 cm

  3. 22 cm

  4. none of the above


Correct Option: A
Explanation:

$\triangle ABC$ is enlarged to $\triangle A'B'C'$,
Thus, $\dfrac{A'B'}{AB} = 3$
$\Rightarrow \dfrac{A'B'}{4} = 3$
$\rightarrow A'B' = 4 \times 3$
$\Rightarrow A'B' = 12 $ cm 

A triangle ABC is enlarged, about the point O as centre of enlargement, and the scale factor is 3. Find OC', if  OC=21 cm.

  1. 63 cm

  2. 53 cm

  3. 43 cm

  4. none of the above


Correct Option: A
Explanation:

$\triangle ABC$ is enlarged to $\triangle A'B'C'$,
Thus, $\dfrac{OC'}{OC} = 3$
$\Rightarrow \dfrac{OC'}{21} = 3$
$\Rightarrow OC' = 21 \times 3$
$\Rightarrow OC' = 63 $ cm

A flagstaff $17.5$ m high casts a shaded length of $40.25$ m. The height of the building which costs a shadow of length $28.75$ m under similar conditions will be:

  1. $10$ m

  2. $12.5$ m

  3. $17.5$ m

  4. $21.25$ m


Correct Option: B
Explanation:

Flagstaff and shade forms right triangle with height $17.5$ m and base $40.25$ m

$\dfrac{17.5}{40.25} = \tan(\theta)$
under similar conditions $\theta$ will remain same.
Lets assume height of the building as $H$
Hence, $ \tan(\theta)=\dfrac{17.5}{40.25}$ $ = \dfrac {H}{20.75}$
$\Rightarrow  H= 12.5$ m

The ratio of the lengths of the corresponding sides of $2$ similar right angled triangles is $2:5$. If the length of the hypotenuse of the smaller triangle is $5$ inches, find the length of the hypotenuse of the larger triangle (in inches):

  1. 2

  2. 2.5

  3. 7

  4. 10

  5. 12.5


Correct Option: E
Explanation:

Ratio of the length of the sides of the two triangle $=2:5$

If hypotenuse  of small triangle $=5$ inches
Let the hypotenuse of  larger triangle $=x$
$\therefore \dfrac{5}{x}=\dfrac{2}{5}$
$\therefore  x=\dfrac{25}{2}=12.5$  inches

If the image of an object is enlarged, then what would be the effect on scale factor, $k?$

  1. $k$ will remain same for both.

  2. $k>1$ for enlarged image.

  3. $k<1$ for enlarged image.

  4. none of the above


Correct Option: B
Explanation:


If image is enlarged, $k>1.$
If image size does not change, then $k=1.$
If image size is reduced, $k<1.$

Maps must have a ......... and a .......... .

  1. legend, scale

  2. scale, map

  3. Scale, legend

  4. none


Correct Option: C
Explanation:

Maps must have a scale and a legend