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. 5)
5.
The greatest number of four digits which is divisible by 15, 25, 40 and 75 is:
9000
9400
9600
9800
Answer: Option
Explanation:

Greatest number of 4-digits is 9999.

L.C.M. of 15, 25, 40 and 75 is 600.

On dividing 9999 by 600, the remainder is 399.

Required number (9999 - 399) = 9600.

Discussion:
120 comments Page 5 of 12.

Sangeet said:   1 decade ago
Hi, I do not when to use HCF & when to use LCM?

Here it is mentioned the word "GREATEST" but still we find LCM instead of HCF why?

Priya said:   1 decade ago
LCM of 15: 5 X 3.

25: 5^2.

40: 5 X 2^3.

75: 5^2 X 3.

From each highest power of 5 = 5^2, 2 = 2^3, 3 = 3.

So 5^2 X 2^3 X 3 = 600.

Vishwa said:   7 years ago
The greatest number given there is first to come.
9800 which is not divisible by 600.
9600 which is divisible,
So answer is 9600.

Gayathri Ganesan said:   1 decade ago
Magesh, I'm also getting confusion with that type of doing lcm brings 3000. Then how they put 600? Is anyone cleared this doubt?

Sruthi said:   1 decade ago
5) 15,25,40,75
------------
5) 3,5,8,15
------------
3) 3,1,8,3
------------
1,1,8,1

Now,

LCM = 5*5*3*8 = 600.

Dileep Kumar M B said:   1 decade ago
How a person could know whether to take LCM or HCF? can anybody explain me when should we use these LCM and HCF ?

Daisy Chowdhury said:   1 decade ago
I use the same technique and I am agree with the first one. Now I am much confident about with dealing the sum.

Manish said:   1 decade ago
Why we have taken LCM of following numbers when the question is about the greatest number which suggests HCF?

Achutha said:   1 decade ago
Please tell why we have to take lcm instead instead of hcf and in which situation I have to take lcm or hcf?

David said:   1 decade ago
Because greatest no. of four digit is only 9999.

So we divide 9999 by 600. So please use your common sense.


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