Aptitude - Logarithm - Discussion
Discussion Forum : Logarithm - General Questions (Q.No. 1)
1.
Which of the following statements is not correct?
Answer: Option
Explanation:
(a) Since loga a = 1, so log10 10 = 1.
(b) log (2 + 3) = log 5 and log (2 x 3) = log 6 = log 2 + log 3
log (2 + 3) 
log (2 x 3)
(c) Since loga 1 = 0, so log10 1 = 0.
(d) log (1 + 2 + 3) = log 6 = log (1 x 2 x 3) = log 1 + log 2 + log 3.
So, (b) is incorrect.
Discussion:
37 comments Page 1 of 4.
Garvit said:
10 years ago
Option D can't be considered answer. It's tricky actually:
LHS:
log (1+2+3) = log 6. [1+2+3 = 6].
RHS:
log1 + log2 + log3 = log (1x2x3) = log 6.
Since LHS = RHS (no matter how it comes) D isn't the option.
LHS:
log (1+2+3) = log 6. [1+2+3 = 6].
RHS:
log1 + log2 + log3 = log (1x2x3) = log 6.
Since LHS = RHS (no matter how it comes) D isn't the option.
Isaac said:
8 years ago
Can someone help me understand how D is a true statement?
If log6=10^6=1,000,000
how is that equal to log1+log2+log3?
=10^1+10^2+10^3,
=10+100+1000,
=1110.
If log6=10^6=1,000,000
how is that equal to log1+log2+log3?
=10^1+10^2+10^3,
=10+100+1000,
=1110.
Yuvatharani said:
5 years ago
According to logarithm formula,
log (xy) = log x + log y but,
log(x+y) is not equal to log x+ log y.
So I think option B and D both are wrong.
log (xy) = log x + log y but,
log(x+y) is not equal to log x+ log y.
So I think option B and D both are wrong.
(7)
Suhaas said:
9 years ago
@Palak Kapoor.
The answer is undefined.
log{5 - 4}[5^2 - 4^2 - 4]
log{1}[25 - 16 - 16]
log[25 - 32]
log[- 7]
log value for -ve is undefined.
The answer is undefined.
log{5 - 4}[5^2 - 4^2 - 4]
log{1}[25 - 16 - 16]
log[25 - 32]
log[- 7]
log value for -ve is undefined.
Riyen said:
4 years ago
We know that a(b+c)=a.b+a.c by distributive property we apply same with log also
log(a+b)=loga + logb is correct.
So, D is also correct.
log(a+b)=loga + logb is correct.
So, D is also correct.
(2)
Murali said:
1 decade ago
243 base 9.
This mainly 243 = 3*3*3*3*3 = 3^5.
And 9 = 3*3 = 3^2.
So answer is 5/2. I dot no how to write log in keyboard.
This mainly 243 = 3*3*3*3*3 = 3^5.
And 9 = 3*3 = 3^2.
So answer is 5/2. I dot no how to write log in keyboard.
Meenakshi said:
9 years ago
The anwer is absolutely correct according to log properties.
It's log a + log b = log(a * b).
not log(a + b) = log(ab).
It's log a + log b = log(a * b).
not log(a + b) = log(ab).
Riya Raj said:
7 years ago
I'm also confused because it both the cases results are coming the same soo however it's different. Please explain me.
Vikash said:
1 decade ago
log 6 = log(2*3) = log 2 + log 3.
But log(2+3) =log 5 which is not equal to log 6.
So, log(2+3) != log 2 + log 3.
But log(2+3) =log 5 which is not equal to log 6.
So, log(2+3) != log 2 + log 3.
(1)
Komali said:
1 year ago
I think B is also correct.
log (a +b) = loga + log b.
log a +log b = log ( a×b).
* log ( a +b )= log (a×b).
log (a +b) = loga + log b.
log a +log b = log ( a×b).
* log ( a +b )= log (a×b).
(3)
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