Question

given that x is a random five digit natural number y = x^4 +4 , what us the probability that y us not divisible by 5?

Answer 1

Answer:

x⁴ is always even for all x belongs to R. So, x⁴+4 is also even. But a even number is divisible by 5, when it had unit digit 0 only. So, unit digit of x⁴ should be 6. So, x must be even. But all even numbers are not divisible by 5.

Any unit digit in a even number will contain 0 or 2 or 4 or 6 or 8. Here, only 0 is required.

So, Probability that y is divisible by 5 = 1/5.

So, Probability that y is not divisible by 5

= 1 - 1/5 = 4/5

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