Aptitude - Problems on H.C.F and L.C.M - Discussion

Discussion Forum : Problems on H.C.F and L.C.M - General Questions (Q.No. 7)
7.
Three number are in the ratio of 3 : 4 : 5 and their L.C.M. is 2400. Their H.C.F. is:
40
80
120
200
Answer: Option
Explanation:

Let the numbers be 3x, 4x and 5x.

Then, their L.C.M. = 60x.

So, 60x = 2400 or x = 40.

The numbers are (3 x 40), (4 x 40) and (5 x 40).

Hence, required H.C.F. = 40.

Discussion:
41 comments Page 4 of 5.

P.vinothini said:   1 decade ago
Please if you don't mine reply what is mean by co-prime?

Sanjay said:   1 decade ago
Can this approach be applied for any higher co-prime numbers ?

Karan said:   1 decade ago
Better way to find hcf for three numbers is either you could take the differences between them respectively.

Brajesh said:   1 decade ago
If h.c.f is given then just do 3*4*5=60 and then 6o*40(h.c.f given)=2400

Rahul said:   1 decade ago
If given HCF what can I do. ?

Achu said:   1 decade ago
Easy method
3*4*5 = 60
2400/60 = 40

Anurag said:   1 decade ago
@shrimant....

The formula works only for two number..for eg take num
2,4,8....hcf is 2

lcm is 16.

product of hcf and lcm=32

product of num=64.

Shrimant said:   1 decade ago
In the explanation answer,the formula has been used is
Factor of number 3x={3,x}
Factor of number 4x={4,x}
Factor of number 5x={5,x}
Therefore,LCM is a product of {3,4,5,x} [x has taken once as it is common] i.e.LCM=60x
60x=2400
x=40
But,
If we take another formula that
Product of all numbers = Product of LCM and HCF
3x*4x*5x=2400*x
60x3[x to the power 3 or x cube]=2400x
x3[x to the power 3 or x cube] 2400
------------------------------ = ------
x 60
x2[x to the power 2 or x square]=40

therefore, x= square root of 40
then?
Can anybody solve my query???

MKR said:   1 decade ago
600,800,1000 commom divisor is :200

600)800(1
600
---------
200)600(3
600
---------------
0
---------

200)1000(5
1000
-------
0
----------


so 200 is the H C F.............

Vicky said:   1 decade ago
Can anyone say if instead H.C.F is given in place of L.C.M.

And asked to find L.C.M?


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