web2.0calc
 

Melody

avatar
यूजर का नामMelody
स्कोर118691
Membership
Stats
सवाल 900
जवाब 33647

-6
837
3
avatar+118691 

WELCOME BACK CPHILL !


●●●
Melody  11 Feb 2022
 #20
avatar+118691 
0
Walt:

If the last 2 digits of a number are a multiple of 4, the whole number is divisible by 4. For example, 5784 is divisible by 4 because the last 2 digits, 84 is a multiple of 4.


[size=150]Excellent Walt. That is what I wanted![/size]
The reason this is so is as follows.
100 is divisable by 4 therefore any multiple of 100 is divisable by 4.
For example
1537930 = 1537900 + 30
I know that 100 is divisable by 4 therefore
1537900 must be divisable by 4
Therefore the whole great long number will be divisable by 4 if and only if the last 2 digits, 30 are divisable by 4
---------------------------------------------------------------------------------------------------------------------------
The summer Olympics are feld every 4 years. It is easy to know if it is an Olympic year because the last digits of the year will be divisable by 4.
For instance, 1980 80 is exactly divisable by 4 so this was a summer olympics year
---------------------------------------------------------------------------------------------------------------------------

Continuing with this type of logic can you tell me how you could tell fairly easily if a big number was exactly divisable by 8

---------------------------------------------------------------------------------------------------------------------------

Now for the divisability checks. What do we have so far?

1) We have Zamarronics's formula,

2) A number is exactly divisable by 10 if it has a zero at the end. (the last digit is zero)

3) A number is exactly divisable by 2 if it is even.

4) If a number is prime then it is only exactly divisable by 1 and itself

5) A number is exactly divisable by 5 if it ends in 0 or 5

6) A number is exactly divisable by 3 if the sum of its digits is exactly divisable by 3.

7) A number is exactly divisable by 9 if the sum of its digits is exactly divisable by 9

8) If the last 2 digits of a number are a multiple of 4, the whole number is exactly divisible by 4.
24 Jan 2014