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Thought-Process to Discover Knowledge

Welcome to nubtrek.

Books and other education websites provide "matter-of-fact" knowledge. Instead, nubtrek provides a thought-process to discover knowledge.

In each of the topic, the outline of the thought-process, for that topic, is provided for learners and educators.

Read in the blogs more about the unique learning experience at nubtrek.continue

In this page, a simple overview of the divisibility test for `5` is provided.



click on the content to continue..

Which of the following are multiples of `5`?

  • `5,10,15,20,25, cdots`
  • `5,10,15,20,25, cdots`
  • `11,22,33,44,cdots`

The answer is "`5,10,15,20,25, cdots`".

Consider the multiples of `5` given as `5,10,15,20,25, cdots`. Is there any similarity observed in the multiples?

  • all are ending in `0` or `5`
  • all are ending in `0` or `5`
  • there is no similarity observed

The answer is "all are ending in `0` or `5`"

The multiples of `5` has either `5` or `0` in the units place.

Explanation for the curious mind

A large number like `2344` can be given as `234xx10+4`.

It was learned that if one addend is divisible, then the divisibility is decided by the other addend.

`234xx10` is divisible by `5` as `10=5xx2`.

So, the divisibility test is done on the last digit, that is the units digits. In the units digit the possible values are `5` and `0`.

Consider `10` and `25`. Which of these is divisible by `5`?

  • `10`
  • `25`
  • both the above
  • both the above

The answer is "both `10` and `25`"

Test for Divisibility by `5` : If the units digit is `5` or `0`, then the number is divisible by `5`.

Is `2018` divisible by `5`?

  • Yes
  • No
  • No

The answer is "No". Checking the digit in units place `8`, it is concluded that the number is not divisible by `5`.

Is `920` divisible by `5`?

  • Yes
  • Yes
  • No

The answer is "Yes". Checking the digit in units place `0`, it is concluded that the number is divisible by `5`.

                            
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