1.

The probability that the sum of squares of two non-negative integers is divisible by 5 is(a)  7/25(b)  8/25(c)   9/25(d)  2/25

Answer»

Correct option   (c)   9/25

Explanation:

Let two non-negative integers be x & y such that x = 5a + α and y = 5b  + β where 0 ≤ α,  β

New, x+ y2 = 25(a+ b2 ) + 10(aα + bβ)+ α2 + β2

α2 + βshould be divisible by 5

(α ,β) can have ordered pairs as

{(0,0), (1,2), (2,1), (1,3), (3,1), (2,4), (4,2), (3,4), (4,3)} = 9 ways

 required probability is 9/25



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