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

Divide the series by 3 I get 4 5 20 18.

Further divide by a 4, 1 5 5 18. Again divide by 5 I end up with 1 1 1 18 now I get lcm = 1080. Am I right?

2|12 15 20 54.
2|06 15 10 27.
3|03 15 05 27.
5|01 05 05 09.
9|01 01 01 09.
|01 01 01 01.

Best to find LCM solve till all value get 1.

You will always get perfect answer without confusion.

2*2*3*5*9 = 540.

LCM of 12, 15, 20, 24 is 540. Required no is 548. 548 is divided by 12, 15, 20, 24 respectively. The remainder is 8. That is the reason add 8.

Dividend = Divisor * Quotient + Remainder.

That's why +8.

Yes why it is not 540k+8?

@Fia.

The LCMof the number is 48 .plus add remainder 7 = 55.
Answer is 55.

Why are we adding 8 with the lcm I don't get that because in some cases we do subtract the remainder from the lcm so could someone please help me out with this?

@unknown.

Given nor.s in increasing order:12,15,20,54
At the beginning take first two numbers are;

Then do division operation i.e
12)15(1
12
________
03)12(4
12
_________
0(remainder )

If remainder becomes 0,then take divisor of last operation, i.e 3
Now division operation b/ w 3 and 20
3)20(6
18
____
2)3(1
2
______
1)2(2
2
____
0

Similarly now proceed with 1 n 54
1)54(54
54
___
0
.: last divisor 1 is the required H.C.F.

Please tell me how to find the HCF of 15, 12, 20, 54.

Yes @Jalpan even I am confused as to when you need to subtract and when you need to add the remainder. Can anyone explain?