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. 29)
29.
| The H.C.F. of | 9 | , | 12 | , | 18 | and | 21 | is: |
| 10 | 25 | 35 | 40 |
Answer: Option
Explanation:
| Required H.C.F. = | H.C.F. of 9, 12, 18, 21 | = | 3 |
| L.C.M. of 10, 25, 35, 40 | 1400 |
Discussion:
31 comments Page 2 of 4.
Swarn Aabha Sao said:
4 weeks ago
HCF = HCF (9,12,18,21)/LCM(10,25,35,40) = 3/1400.
HCF --> common primes with smallest power.
HCF(9,12,18,21 )= 3.
9 = 3 x 3.
12 = 2 x 2 x 3.
18 = 2 x 3 x 3.
21 = 3 x 7.
Highest common factor in all four numbers = 3
LCM --> all primes with largest power
LCM(10,25,35,40)= 1400
10 = 2 x 5
25 = 5 x 5
35 = 5 x 7
40 = 2 x 2 x 2 x 5
So,the highest power of each prime = 2 x 2 x 2 x 5 x 5 x 7.
= 8 x 25 x 7.
= 200 x 7.
= 1400.
HCF --> common primes with smallest power.
HCF(9,12,18,21 )= 3.
9 = 3 x 3.
12 = 2 x 2 x 3.
18 = 2 x 3 x 3.
21 = 3 x 7.
Highest common factor in all four numbers = 3
LCM --> all primes with largest power
LCM(10,25,35,40)= 1400
10 = 2 x 5
25 = 5 x 5
35 = 5 x 7
40 = 2 x 2 x 2 x 5
So,the highest power of each prime = 2 x 2 x 2 x 5 x 5 x 7.
= 8 x 25 x 7.
= 200 x 7.
= 1400.
Sarmila said:
1 month ago
The answer should be 3/2800.
Because,
H.C.F of 9, 12, 18, 21 is 3.
L.C.M of 10, 25, 35, 40 is 2800.
So, the answer is 3/2800.
Because,
H.C.F of 9, 12, 18, 21 is 3.
L.C.M of 10, 25, 35, 40 is 2800.
So, the answer is 3/2800.
Saidaiah said:
7 years ago
The Lcm is 3/2800.
Gopal said:
8 years ago
For the same question instead of hcf if LCM was asked what will be the answer? Please solve it.
Amir said:
9 years ago
If we take LCM collectively, the HCF is 2 and 3, if one by one it's 3. How can we recognise that the HCF should be taken separately?
Amit said:
9 years ago
Answer Should be 3/2800.
Because,
H.C.F of 9, 12, 18, 21 is 3.
L.C.M of 10, 25, 35, 40 is 2800.
So, the answer is 3/2800.
Because,
H.C.F of 9, 12, 18, 21 is 3.
L.C.M of 10, 25, 35, 40 is 2800.
So, the answer is 3/2800.
Sanjuu s said:
10 years ago
Simply
Here HCF of 9 =3 * 3, 12 = 3 * 2 * 2, 18 = 3 * 3 * 2, and 21 = 3 * 7.
HCF = 3.
LCM of 10 =2 * 5, 25 = 5* 5, 35 = 3 * 7, 40 = 2* 2 * 2 * 5.
LCM = 1400.
Required HCF = HCF/LCM.
= 3/1400.
Here HCF of 9 =3 * 3, 12 = 3 * 2 * 2, 18 = 3 * 3 * 2, and 21 = 3 * 7.
HCF = 3.
LCM of 10 =2 * 5, 25 = 5* 5, 35 = 3 * 7, 40 = 2* 2 * 2 * 5.
LCM = 1400.
Required HCF = HCF/LCM.
= 3/1400.
Bhushan said:
2 decades ago
Is this the correct answer?
Lalu said:
10 years ago
Thats long process, tell me short cut method.
Mozzima said:
1 decade ago
Why we have taken LCM of denominator?
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