Question

Among the following numbers, which number is divisible by 7?
A. 654
B. 672
C. 542
D. 321

Answer 1

Hint: Apply the condition for divisibility by 7 for all the options and verify the results. The condition for divisibility by 7 is as follows:
Remove the last digit or units place, double it and subtract it from the truncated original number i.e.(tens , hundreds , thousands and so on except units digit) and continue this until only one digit remains and if it is multiple of 7, then the original number is divisible by 7.

Complete step by step answer:
We’ll proceed by hit and trial method by picking the options given.
Firstly,
Let’s check option A) 654
Unit’s digit or last digit = 4
Truncated number = 65
\[65 - 4 \times 2 = 57{\text{ ,not divisible by 7}}\]
We see that it is a never ending process . Therefore , we can conclude it is not divisible by 7.
Let’s check option B) 672
Unit’s digit or last digit = 2
Truncated number = 67
$67 - 2 \times 2 = 63{\text{ ,divisible by 7}}$

So, the correct answer is “Option B”.

Note: Such similar questions can be asked for divisibility conditions by other numbers as well. Therefore , It is advisable to remember the divisibility condition for different natural numbers. Such questions are also asked in aptitude tests, Olympiads etc.