Elitmus
Exam
Numerical Ability
Log and Antilog
if a,b,c given a G.P. (loga+logb+logc)/log6=6.and (b-a) always given a perfect cube no.what the value of a+b+c
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- a,b,c are in g.p. so,
b^2 = ac
2logb=loga +logc
(loga+logb+logc)/log6=6
put value
(2logb+logb)/log6=6
3logb=6log6
logb=2log6
logb=log6^2
logb=log36
b=36
(b-a) is perfect cube so (36-9)=27
a=9
b^2=ac
c=36*36/9
c=144
a+b+c=9+36+144=189 - 6 years agoHelpfull: Yes(19) No(3)
- option please?
- 6 years agoHelpfull: Yes(1) No(1)
- solve (#M40165599) coins questions
- 6 years agoHelpfull: Yes(1) No(0)
- a, b, and c are in GP.
So b=ar
c=ar^2;
So log a+logb+logc=loga+log(ar)+log(ar^2)
=3loga+3logr=3log(ar)
So 3log(ar)/log6=6
Log(ar)/log6=2
ar=36
b=36
b-a is a perfect cube, let's say 27
Therefore 36-a=27
a=9
r=4
a+b+c=9+36+9*4*4=189 - 5 years agoHelpfull: Yes(1) No(0)
- (a)189 (b)49 (c)69 (d)100
- 6 years agoHelpfull: Yes(0) No(0)
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