Test of Divisibility : Number Properties
The question is a Number Systems and number theory question on test of divisibility.
Question
10
25 - 7 is divisible by
- 2
- 3
- 9
- Both (2) and (3)
Correct Answer -
3. Choice (2)
Explanatory Answer
To find the number of factors of a given number, express the number as a product of powers of prime numbers.
10
25 - 7 = (10
25 - 1) - 6
The number 10
25 - 1 = 99.....9 (25 digits) is divisible by 3.
Therefore, (10
25 - 1) - 6 = (24 nines and unit digit is 3) 99.......93.
This number is divisible by 3 (from amongst the given choices).
Correct answer choice (2)
Level of difficulty : Moderate
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