Each coefficient in the equation `a x^2+b x+c=0` is determined by throwing an ordinary six faced die. Find the probability that the equation will have real roots.

Explanation

Roots are real when `b^2=4ac`

`implies (b/2)^2=ac`

When `b=1, (b/2)^2=1/4`

When `b=2, (b/2)^2=1`

When `b=3, (b/2)^2=9/2`

When `b=4, (b/2)^2=4`

When `b=5, (b/2)^2=25/2`

When `b=6, (b/2)^2=9`

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