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Answers
>> n is a positive integer
>> Numbers :- n , n+4 , n+8 , n+12, n+16
• To show that only one of the number above is divisible by 5
>> Any number is divisible by 5 if it is in the form of 5(x) , where x is any integer
(for the integer value)
>>Then the numbers should be multiple of 5
•Let us consider that out of Numbers :-
n , n+4 , n+8 , n+12, n+16
n is divisible by 5 = 5x
•Then we will check divisibility of other numbers
for
> n+4 = 5x + 4 [which is not a multiple of 5]
> n+8 = 5(x+1) + 3 [which is not a multiple of 5]
> n+12 = 5(x+2) + 2 [which is not a multiple of 5]
> n+16 = 5(x+3) + 1 [which is not a multiple of 5]
>> Similarly we can also conclude that if one them is a multiple of "5" then others will not fulfill the condition to be divisible by 5
>> Hence ,Shown that only one Number out of Numbers :- n , n+4 , n+8 , n+12, n+16 is divisible by 5 .
SOLUTION
Any positive integer will be of form 5q,5q+1,5q+2,5q+3,or 5q+4
Case 1
If n= 5q
n is divisible by 5
Now, n= 5q
=) n+4= 5q+4
The number (n+4) will leave remainder 4 when divided by 5.
Again, n= 5q
=) n+8=5q+8= 5(q+1)+3
The number (n+8) will leave remainder 3 when divided by 5.
Again, n= 5q
=) n+12=5q+12= 5(q+2)+2
The number (n+12) will leave remainder 2 when divided by 5.
Again, n= 5q
=)n+16= 5q+16= 5(q+3)+1
The number (n+16) will leave remainder 1 when divided by 5.
Case 2
When, n= 5q+1
The number n will leave remainder 1 when divided by 5.
Now, n= 5q+1.
=) n+2= 5q+3
The number (n+2) will leave remainder 3 when divided by 5.
Again, n= 5q+1
=)n+4=5q+5= 5(q+1)
The number (n+4) will be divisible by 5.
Again, n= 5q+1
=) n+8= 5q+9= 5(q+1)+4
The number (n+8) will leave remainder 4 when divided by 5.
Again, n= 5q+1
=) n+12= 5q+13= 5(q+2)+3
The number (n+12) will leave remainder 3 when divided by 5.
Again, n= 5q+1
=) n+16= 5q+17= 5(q+3)+2
The number (n+16) will leave remainder 2 when divided by 5.
Similarly, we can check the results for 5q+2, 5q+3 and 5q+4.
In each case only one out of n, n+2,n+4, n+8, n+16 will be divisible by 5.
HOPE it helps ✔️