Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 21)
21.
Which of the following number is divisible by 24 ?
Answer: Option
Explanation:
24 = 3 x8, where 3 and 8 co-prime.
Clearly, 35718 is not divisible by 8, as 718 is not divisible by 8.
Similarly, 63810 is not divisible by 8 and 537804 is not divisible by 8.
Consider option (D),
Sum of digits = (3 + 1 + 2 + 5 + 7 + 3 + 6) = 27, which is divisible by 3.
Also, 736 is divisible by 8.
3125736 is divisible by (3 x 8), i.e., 24.
Discussion:
56 comments Page 2 of 6.
Raj said:
7 years ago
Why are we taking 3 and 8 only and not 4, 6 or 12, 2?
(1)
Ashwin said:
8 years ago
24 = 2 * 3 * 4 the given numbers compulsory divisible by 2, 3 and 4.
The option checks to all.
All option divisible 2.
The two option divisible 3 (537804 and 3125736).
The one option divisible 4 (3125736).
So 2, 3, 4 are divisible by 3125736. it is the correct answer.
Clear EXPLANATION:
2 divisible law.
Rule: If it ends with a 0, 2, 4, 6, or 8.
3 divisible law.
Rule: If the sum of the digits is a multiple of 3.
Number-----> Divisible -----> Reason
405-----> Yes-----> 4 + 0 + 5 = 9 (9 is a multiple of 3).
381-----> Yes-----> 3 + 8 + 1 = 12 (12 is a multiple of 3).
928-----> No -----> 9 + 2 + 8 = 19 (19 is not a multiple of 3).
4,616-----> No -----> 4 + 6 + 1 + 6 = 17 (17 is not a multiple of 3).
4 divisible law.
Rule: If the last two digits are a multiple of 4 (or if the last two digits are 00)
Number ----> Divisible ----> Reason
348 -----> Yes-----> 48 is a multiple of 4.
27,616 -----> Yes-----> 16 is a multiple of 4.
8,514 -----> No -----> 14 is not a multiple of 4.
722 -----> No-----> 22 is not a multiple of 4.
1,200-----> Yes -----> The last two digits are 00.
200 is a multiple of 4.
THANK YOU.
The option checks to all.
All option divisible 2.
The two option divisible 3 (537804 and 3125736).
The one option divisible 4 (3125736).
So 2, 3, 4 are divisible by 3125736. it is the correct answer.
Clear EXPLANATION:
2 divisible law.
Rule: If it ends with a 0, 2, 4, 6, or 8.
3 divisible law.
Rule: If the sum of the digits is a multiple of 3.
Number-----> Divisible -----> Reason
405-----> Yes-----> 4 + 0 + 5 = 9 (9 is a multiple of 3).
381-----> Yes-----> 3 + 8 + 1 = 12 (12 is a multiple of 3).
928-----> No -----> 9 + 2 + 8 = 19 (19 is not a multiple of 3).
4,616-----> No -----> 4 + 6 + 1 + 6 = 17 (17 is not a multiple of 3).
4 divisible law.
Rule: If the last two digits are a multiple of 4 (or if the last two digits are 00)
Number ----> Divisible ----> Reason
348 -----> Yes-----> 48 is a multiple of 4.
27,616 -----> Yes-----> 16 is a multiple of 4.
8,514 -----> No -----> 14 is not a multiple of 4.
722 -----> No-----> 22 is not a multiple of 4.
1,200-----> Yes -----> The last two digits are 00.
200 is a multiple of 4.
THANK YOU.
(1)
Ronit said:
8 years ago
Why we take only 8*3=24? why not other?
Thiru said:
9 years ago
What is co-Prime?
Keerthi said:
8 years ago
35718 can be divisible by 3 and 8 then why can't we divide with 24?
Prakarsh said:
8 years ago
We can not take 2*3*4 because 2&4 are not co primes, hence for 24 only possible co-primes are 8*3.
CO-PRIME: Those prime numbers which have only '1' as a common factor.
THANK YOU
CO-PRIME: Those prime numbers which have only '1' as a common factor.
THANK YOU
Amit Thakuri said:
9 years ago
@Somgopal.
Will you make me understand how did we got 736 and from where?
Will you make me understand how did we got 736 and from where?
Neha said:
9 years ago
@Thiru.
A set of numbers which do not have any other common factor other than 1 are called co-prime.
A set of numbers which do not have any other common factor other than 1 are called co-prime.
Neha said:
9 years ago
Thanks @Naresh.
Yogi said:
9 years ago
I don't understand the methods. Please anyone tell me the shortcut method for solving this.
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