Elitmus
Exam
Numerical Ability
Log and Antilog
if logN base3+logN base9,sum is whole number,then how many number possible for N between 100 to 100?
A)1
B)20
C)111
D)i didn't remember
Read Solution (Total 5)
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- ans =1
N value should be in between 10 to 100
log 81 base 3 + log 81 base 9 is possible
- 9 years agoHelpfull: Yes(17) No(0)
- answer should be option (A)
we can write logN base3=(logN baseX/log3 baseX);
and logN base9=(logN baseX/log9 baseX);
now, logN base3+logN base9= ( logN baseX / log3 baseX + logN baseX / log9 baseX)
=logN baseX (1/log3 baseX + 1/2log3 baseX) bcz (3 square =9)
=logN baseX ( 3log3 baseX / 2log3 baseX *log3 baseX) by simple addition
=logN base X ( 3/2log3 base X)
or =logN base X *3 / log9 base X
or =3 * logN base 9:
so N should be 81 because it is a 9 square and it also ies between 10 to 100. - 9 years agoHelpfull: Yes(7) No(0)
- answer should be 2
since log(9)+log(9)=3 for base 3 and 9 respectively
log 81+ log 81=6 for base 3 and 9 respectively - 9 years agoHelpfull: Yes(4) No(2)
- ans=1 because 81 is only value between 10 to 100
- 9 years agoHelpfull: Yes(1) No(0)
- @akshay value must be in range {10 to 100 }
- 9 years agoHelpfull: Yes(1) No(1)
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