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Diagonal of cube and cuboid - class-X

Description: diagonal of cube and cuboid
Number of Questions: 18
Created by:
Tags: surface area and volume of cube and cuboid surface area and volume of solids surface area and volume maths mensuration
Attempted 0/18 Correct 0 Score 0
Is $(3,\,4,\,6)$ a pythagorean triplet?
  1. Yes

  2. No

  3. Cannot be deermined

  4. None


Correct Option: B
Explanation:

$ {3}^{2} + {4}^{2} = 9 + 16 = 25 $
$ {6}^{2} = 36 $

Since, $  {3}^{2} + {4}^{2} \neq {6}^{2} , (3,4,6) $ is not a pythagorean triplet.

To get _________ triplets we use the general form $ 2m, m^2+1, m^2-1$.

  1. Square number

  2. Consecutive number

  3. Repeated

  4. Pythagorean


Correct Option: D
Explanation:

$ 2m, m^2+1, m^2-1$ forms are used to get Pythagorean Triplets.

Are all of the following triplets are pythagorean?
$(8,\,15,\,17)$
$(16,\,63,\,65)$
$12,\,16,\,20$

  1. Yes

  2. No

  3. Cannot be determined

  4. None


Correct Option: A
Explanation:

To check if the set of numbers $ {a,b,c} $are Pythagorean triplets, we need to check if $ {a}^{2} + {b}^{2} = {c}^{2} $

1) For $ {8,15,17} $
$ {8}^{2} + {15}^{2} = 64 + 225 = 289 $
and $ {17}^{2} = 289 $
Hence, $ {8}^{2} + {15}^{2} = {17}^{2} $

2) For $ {16,63,65} $
$ {16}^{2} + {63}^{2} = 256 + 3969 = 4225 $
and $ {65}^{2} = 4225 $
Hence, $ {16}^{2} + {63}^{2} = {65}^{2} $

3)For $ {12,16,20} $
$ {12}^{2} + {16}^{2} = 144 + 256 = 400 $
and $ {20}^{2} = 400 $
Hence, $ {12}^{2} + {16}^{2} = {20}^{2} $

Thus, the given set of numbers are Pythagorean triplets.

Write the Pythagorean triplet whose one member is 30.

  1. $226$ and $224$

  2. $220$ and $222$

  3. $227$ and $229$

  4. None of these


Correct Option: A
Explanation:

Solution:

General form of pythagorean triplets are $m^2-1,2m,m^2+1$

$\Rightarrow$First member of triplet $a=2m=30\Rightarrow m=15$


Since, it is even 
$\Rightarrow$So, second member of triplet $b=\left(m\right)^2-1=15^2-1=225-1=224$

$\Rightarrow$And third member of triplet $c=m^2+1=225+1=226$

Hence, $A$ is the correct option.

Find the pythagorean triplet.

  1. $12,35,37$

  2. $12,36,37$

  3. $12,43,47$

  4. None of these


Correct Option: A
Explanation:

Every right triangle has side length satisfying:

a$^{2}$ $+$ b$^{2}$ $=$ c$^{2}$
c is the longest side,
Here 
$12^{2}$ $+$ $35^{2}$ $=$ $37^{2}$
Hence it is a pythagorean triplet.
Option A is correct.

A lady went for a walk and she was walking in a right triangular park. The tiles of the smallest side were visible while other 2 sides she couldn't make out. Each tile was 1 m. The length of the visible side was 10 m. Help the lady to find the length of the other 2 sides , so she could calculate what distance she is walking everyday. 

  1. 14 m and 16 m

  2. 22 m and 23 m

  3. 24 m and 26 m

  4. 42 m and 46 m


Correct Option: C
Explanation:

one side$=10 m$

Other two sides and 10 m should be Pythagorean triplet in order to form right triangle.
$14^{2}$$+$$10^{2}$$=$$296$
$22^{2}$$+$$10^{2}$$=$$584$

$24^{2}$$+$$10^{2}$$=$$576$
$576$$=$$26^{2}$
$42^{2}$$+$$10^{2}$$=$$1864$
Hence, Option C is correct.

Find the pythagorean triplet.

  1. $8, 15, 17$

  2. $9, 10, 15$

  3. $9, 10, 17$

  4. None of these


Correct Option: A
Explanation:

Every right triangle has side length satisfying:

a$^{2}$ $+$ b$^{2}$ $=$ c$^{2}$
c is the longest side,
Here 
$8^{2}$ $+$ $15^{2}$ $=$ $17^{2}$
Hence it is a pythagorean triplet.
Option A is correct.

Write the Pythagorean triplet whose one member is $24$.

  1. $143$ and $145$

  2. $133$ and $144$

  3. $112$ and $115$

  4. $324$ and $325$


Correct Option: A
Explanation:

Using  $ 2m, m^2+1, m^2-1$ forms

 Let us take $2m = 24$

$m=\dfrac{24}{2}=12$

if $m = 12, m^2-1=12^2= 144-1 =143$

if $ m = 12, m^2 +1=12^2= 144+1 =145$

Therefore, option A is the correct answer.

Find the Pythagorean triplet whose one member is $18$.

  1. $28$ and $20$

  2. $80$ and $82$

  3. $72$ and $92$

  4. $34$ and $54$


Correct Option: B
Explanation:

Using  $ 2m, m^2+1, m^2-1$ forms 
Let us take $2m = 18$
           

$m=\dfrac{18}{2}=9$

if $m = 9, m^2-1=9^2= 81-1 =80$
if $ m = 9, m^2 +1=9^2= 81+1 =82$
Therefore, B is the correct answer.

What is the value of x, if (7, x, x - 2) is a Pythagorean triple?

  1. -11.25

  2. 26.5

  3. -16.5

  4. 16.5


Correct Option: A
Explanation:

Applying the Pythagorean triples rule as $a^{2}+b^{2}= c^{2}$
$7^{2}+x^{2}= (x - 2)^{2}$
49 + $x^{2}$ = $x^{2}$+ 4 -4x
Both the side $x^{2}$ will get cancelled,
45 = -4x
x = -11.25

What is the value of x, if (5, x, 13) is a Pythagorean triple?

  1. 10

  2. 11

  3. 12

  4. 13


Correct Option: C
Explanation:

Applying the Pythagorean triples rule as $a^{2}+b^{2}= c^{2}$
$5^{2}+x^{2}= 13^{2}$
25 + $x^{2}$ = 169
$x^{2}$ = 169 - 25
$x^{2}$ = 144
Squaring on both the sides, we get
x = 12.

Which one of the following is not a Pythagorean triples?

  1. 11, 60, 61

  2. 16, 63, 65

  3. 28, 45, 53

  4. 30, 80, 89


Correct Option: D
Explanation:

Applying the Pythagorean triples rule as $a^{2}+b^{2}= c^{2}$
Option A: $11^{2}+60^{2}= 61^{2}$
= 121 + 3600 = 3721 is a Pythagorean triples
Option B: $16^{2}+63^{2}= 65^{2}$
= 256 + 3969 = 4225 is a Pythagorean triples
Option C: $28^{2}+45^{2}= 53^{2}$
= 784 + 2,025 = 2809 is a Pythagorean triples
Option D: $30^{2}+80^{2}= 89^{2}$
= 900 + 6400 $\neq$ 7921 is not a Pythagorean triples.

Identify the Pythagorean triples.

  1. 5, 12, 13

  2. 8, 24, 25

  3. 11, 61, 61

  4. 20, 70, 10


Correct Option: A
Explanation:

Applying the Pythagorean triples rule as $a^{2}+b^{2}= c^{2}$
Option A: $5^{2}+12^{2}= 13^{2}$
25 + 144 = 169
169 = 169 is a Pythagorean triples.

Find the Pythagorean triplets, whose one member is $22.$

  1. $22, 183, 185$

  2. $22, 483, 485$

  3. $22, 23, 25$

  4. $22, 120, 122$


Correct Option: D
Explanation:

For any natural numbers m > 1, $2m, m^{2} - 1$, $m^{2} + 1$ form a Pythagorean triplet.
If we take $m^2 + 1 = 22$, then $m^2 = 21$
The value of m will not be an integer.
If we take $m^2 - 1 = 22$, then $m^2 = 23$
Again the value of m will not be an integer.
Let $2m = 22$
$m = \cfrac{22}{2}$
$m = 11$
$2m = 2 \times 11 = 22$
$m^{2} - 1$ = $11^{2} - 1$
$= 121 - 1 = 120$
$m^{2} + 1$ = $11^{2} + 1$
$= 121 + 1 = 122$
Therefore, the Pythagorean triplets are $ 22, 120, 122.$

Which one of the following is not a Pythagorean triplets?

  1. $7, 24, 25$

  2. $15, 112, 113$

  3. $10, 24, 26$

  4. $14, 12, 13$


Correct Option: D
Explanation:

$14, 12, 13$ is not a Pythagorean triplet.
On squaring, we get
$12^2 + 13^2\ and\ 14^2$
$144 + 169 \ and\ 196$
$313 \neq 196$

What is the Pythagorean triplet, whose one member is $34$?

  1. $34, 278, 290$

  2. $34, 288, 291$

  3. $34, 288, 290$

  4. $35, 288, 290$


Correct Option: C
Explanation:

For any natural numbers m > 1, $2m, m^{2} - 1$, $m^{2} + 1$ forms a Pythagorean triplet.
If we take $m^2 + 1 = 34$, then $m^2 = 33$
The value of m will not be an integer.
If we take $m^2 - 1 = 34$, then $m^2 = 35$
Again the value of m will not be an integer.
Let $2m = 34$
$m = \dfrac{34}{2}$
$m = 17$
$2m = 2 \times 17 = 34$
$m^{2} - 1$ = $17^{2} - 1$
$= 289 - 1 = 288$
$m^{2} + 1$ = $17^{2} + 1$
$=289 + 1 = 290$
Therefore, the Pythagorean triplets are $34, 288, 290.$

Which one of the following is not a Pythagorean triplet?

  1. $7, 24, 25$

  2. $15, 114, 115$

  3. $27, 364, 365$

  4. $6, 8 10$


Correct Option: B
Explanation:

$15, 114, 115$ is not a Pythagorean triplet.
On squaring, we get
$15^2 + 114^2 \ and \ 15^2$
$225 + 12996 \ and \  13225$
$13221 \neq 13225$

A Pythagorean triplet whose smallest member is $8$, is:

  1. $8, 15, 18$

  2. $8, 13, 16$

  3. $8, 14, 17$

  4. $8, 15, 17$


Correct Option: D
Explanation:

We can get Pythagorean triplet by using general form $2m,\ m^{2}-1,\ m^{2}+1 $
Let us first take 

$m^{2}-1=8$
So, $m^{2}=8+1=9$
Which gives $m=3$
Therefore $2m=6$ and  $ \displaystyle m^{2}+1 = 10  $
The triplet is thus $6,8,10$, but $8$ is not the smallest member of this triplet.

So let us try
$2m=8$
then $m=4$
We get $ \displaystyle m^{2}+1 = 16-1=15$
and $ \displaystyle m^{2}+1 =16+1=17$
The triplet is $8,15,17$ with $8$ as the smallest member.

Hence, option $D.$

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