Aptitude - Surds and Indices - Discussion
Discussion Forum : Surds and Indices - General Questions (Q.No. 5)
5.
If 3(x - y) = 27 and 3(x + y) = 243, then x is equal to:
Answer: Option
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.
Discussion:
21 comments Page 2 of 3.
Carol said:
9 years ago
How to solve the y? Don't get it, Please explain it clearly.
Otuboye said:
9 years ago
Please, can you explain clearly how to solve the y?
Harsh said:
8 years ago
How to solve this? Please help me.
EZEKIEL said:
7 years ago
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.
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:
7 years ago
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.
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:
7 years ago
(x-y) + (x+y) = 3+5,
x+x - y-y = 8,
2x-0 = 8,
2x = 8,
x = 8/2,
x = 4.
x+x - y-y = 8,
2x-0 = 8,
2x = 8,
x = 8/2,
x = 4.
(1)
Ednan malik said:
7 years ago
(x-y)+(x+y) = 3+5,
(x+x-y+y) = 8,
2x+0 = 8,
2x = 8,
x = 8/2,
x = 4,
Therefore x=4.
(x+x-y+y) = 8,
2x+0 = 8,
2x = 8,
x = 8/2,
x = 4,
Therefore x=4.
(3)
Vikram Singh said:
7 years ago
5x-5y = 3x+3y
5x-3x = 3y+5y
2x = 8y
X ÷ y = 8 ÷ 2 so,
X = 4,y = 1.
5x-3x = 3y+5y
2x = 8y
X ÷ y = 8 ÷ 2 so,
X = 4,y = 1.
(4)
Shrikanth said:
6 years ago
Thanks all for explaining it.
(2)
Sri said:
4 years ago
1 .3^(x - Y ) = 27.
3^(x - Y ) = 3^3.
Base are equal.
So,
(x - Y ) = 3 --------------------> 1.
2. 3^( x + y ) = 243.
3^( x + y ) = 3^5.
Base are equal,
So,
( x + y ) = 5 --------------------> 2.
Solve 1 & 2.
X + Y = 3.
X - Y = 5.
----------------------
2x. = 8.
X = 8/2.
So,
X = 4.
3^(x - Y ) = 3^3.
Base are equal.
So,
(x - Y ) = 3 --------------------> 1.
2. 3^( x + y ) = 243.
3^( x + y ) = 3^5.
Base are equal,
So,
( x + y ) = 5 --------------------> 2.
Solve 1 & 2.
X + Y = 3.
X - Y = 5.
----------------------
2x. = 8.
X = 8/2.
So,
X = 4.
(3)
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