Aptitude - Numbers - Discussion

Discussion Forum : Numbers - General Questions (Q.No. 31)
31.
On dividing a number by 5, we get 3 as remainder. What will the remainder when the square of the this number is divided by 5 ?
0
1
2
4
Answer: Option
Explanation:

Let the number be x and on dividing x by 5, we get k as quotient and 3 as remainder.

    x = 5k + 3

    x2 = (5k + 3)2

   = (25k2 + 30k + 9)

   = 5(5k2 + 6k + 1) + 4

On dividing x2 by 5, we get 4 as remainder.

Discussion:
37 comments Page 3 of 4.

Neha yadav said:   10 years ago
In the above equation 30K come by algebra formula i.e. (a+b)^2 = a^2+2ab+b^2.
(1)

Shriram deshmukh said:   9 years ago
Dividing number by 5 its means multi of 5.

(5 * 1 + 3) = 8--> 64/5=> rem 4.
(5 * 2 + 3) = 13--> 169/5=>rem 4.
(5 * 3 + 3) = 18--> 324/5=>rem 4.

And so on.

Raja virat said:   9 years ago
Let the number be 23.
When 23 is divided by 5 we get remainder as 3,
Then, square of the number = 23 * 23 = 529.
So, 529/5 = 4.

Kums kutty said:   9 years ago
In problem x is divisable by 5 then the remainder is 3 so we have X/5=3 then find x value X = 5 * 3 = 15.

In problem, they mentioned square of X is divisible by 5 then what is the remainder.
So X value is 15 then it's square is 225 now we divide it by 5.
225/5 = 45, 45/5 = 9, 9/5 = 4 as a remainder.

Ashi said:   9 years ago
@Nil.Dhongde.

The answer is 1.

Bhuiyanislam said:   8 years ago
Difference - remainder = question - 1.
5 - 3 = x - 1.
x = 2 + 1 = 3.
3^2 = 9.
9/5 = 4.

Mohammed said:   8 years ago
How could come 30 k in above equation?

Bhavani said:   8 years ago
@Rajesh Rao.

You explained in a easy way Thank you !
(1)

IKRAMUL said:   7 years ago
The square of this no means 3 *3=9.
And 9/5 rem is for,
Also let a no which divides by 5 rem is 3.
Where 8/5 rem is 3,
The square of this no is 64,
64/5 we get 4 is a rem.
(1)

Bhuvana ram said:   6 years ago
Formula:(Divisor * Quotient) + remainder = Dividend.

So, (5*Q)+3=D ----> (1)
D^2%5=R -----> (2)

Now we substitute equation(1) in (2).

((5*Q)+3)^2%5 = R
Assume Q = 1,
(5+3)^2%5 = R.
(8)^2%5 = R,
64%5 = R,
4 = R.
(2)


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