Aptitude - Surds and Indices - Discussion

Discussion :: Surds and Indices - General Questions (Q.No.5)

5. 

If 3(x - y) = 27 and 3(x + y) = 243, then x is equal to:

[A]. 0
[B]. 2
[C]. 4
[D]. 6

Answer: Option C

Explanation:

3x - y = 27 = 33       x - y = 3 ....(i)

3x + y = 243 = 35       x + y = 5 ....(ii)

On solving (i) and (ii), we get x = 4.


Anu said: (Mar 22, 2011)  
How is (i) and (ii) solved and we get answer as 4??

Anu said: (Jun 23, 2011)  
2x=8; so x=4 ie.,(x+x)(-y+y) (3+5)

Caroline said: (Sep 8, 2011)  
x - y = 3
x + y =5
---------------
2x =8

Therefore, x = 4.

Anju said: (Jul 19, 2013)  
3 (x-y) = 27.

x-y = 27/3.

x-y = 9 ----- (1).

3 (x+y) = 243.

x+y = 243/3.

x+y = 81 ----- (2).

(x+y) = 81.

(x-y) = 9.

-------------

2y = 72.

y = 72/2 = 36.

y = 36.

x-y = 9.

x-36 = 9.

x = 36/9.

x = 4.

Samson said: (Sep 12, 2013)  
x-y = 3
x+y = 5
________
2x = 8
________

2x/2 = 8/2.
x = 8/2.
i.e x = 4.

Mohammed Sani said: (Feb 19, 2014)  
We used simultaneous equation in solving that, we find for x then y before we can get the final answer.

Arjun said: (Mar 27, 2015)  
How we can find the power?

Is there any short technique by which we can find easily?

Poonam Vaidya said: (Feb 19, 2016)  
I can't got this answer.

Please anyone explain it in detail. Why we cut y?

Hani said: (Apr 12, 2016)  
Why 2x is equal to 8?

Shahjahan said: (Aug 15, 2016)  
(x - y) + (x + y) = 3 + 5,

(x + x) - (y + y) = 8,

2x = 8,

x = 4.

Carol said: (Dec 3, 2016)  
How to solve the y? Don't get it, Please explain it clearly.

Otuboye said: (Jan 2, 2017)  
Please, can you explain clearly how to solve the y?

Harsh said: (Jul 18, 2017)  
How to solve this? Please help me.

Ezekiel said: (Nov 21, 2018)  
The simultaneous equation as in;
x-y=3 x1.
x+y=-5 x-1.
y will be 0 which is always ignored after addition, we get;
2x=8.
where x =4.

Olwa said: (Nov 25, 2018)  
This is a simultaneous equation.
x-y= 3 ---> (i)
x+y=5 ---> (ii)

From eqn (i), we first make x the subject by adding y to both sides;
=> x-y+y=3+y,
=> x=3+y ---> (iii).

Substituting value of x from eqn (iii) in eqn (ii),we get
(3+y)+y=5,
=> 3+2y=5,
=> 3-3+2y=5-3,
=> 2y=2,
Therefore, y=1 ---> (iv).

Substituting eqn (iv) in eqn (iii),
=> x=3+1.
Therefore, X= 4.

Ednan Malik. said: (Dec 30, 2018)  
(x-y) + (x+y) = 3+5,
x+x - y-y = 8,
2x-0 = 8,
2x = 8,
x = 8/2,
x = 4.

Ednan Malik said: (Dec 30, 2018)  
(x-y)+(x+y) = 3+5,
(x+x-y+y) = 8,
2x+0 = 8,
2x = 8,
x = 8/2,
x = 4,
Therefore x=4.

Vikram Singh said: (Feb 1, 2019)  
5x-5y = 3x+3y
5x-3x = 3y+5y
2x = 8y
X ÷ y = 8 ÷ 2 so,
X = 4,y = 1.

Shrikanth said: (Aug 7, 2019)  
Thanks all for explaining it.

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