( ⌈ ( ⌈ ( { ⌈ x ⌉ } + ⌈ { x } ⌉ + { x } ) ⌉ + { x } ) ⌉ ) !
Find the value of the expression above, where x is an irrational real number.
If you believe there are multiple values, submit your answer as 12345.
Notations :
⌈ ⋅ ⌉ denotes the ceiling function .
{ ⋅ } denotes the fractional part function .
! denotes the factorial notation. For example, 8 ! = 1 × 2 × 3 × ⋯ × 8 .
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Nice write up, Sambhrant!
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Thank You Sir ! :D
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Great explanation.
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@Ashish Menon – thanks Ashish
Nice coloring :D
This is the best way to do it, nice explanation!
⌈
x
⌉
is always an integer and fracrional function of any integer is always 0. So
{
⌈
x
⌉
}
= 0.
Now,
{
x
}
always lies between 0 and 1. It can be 0 when it is an integer but x being irrational can never give its fractional function as 0. So for any values lying between 0 and 1, the floor function is always 1. So,
⌈
{
x
}
⌉
= 1.
Now,
{
x
}
is always less than 1 but greater than 0 for any irrational number as explained above. So, its value is 0.something.
So, evaluating the inner bracket,
{
⌈
x
⌉
}
+
⌈
{
x
}
⌉
+
{
x
}
= 1.something. Now, the floor of this value is 2. So,
⌈
(
{
⌈
x
⌉
}
+
⌈
{
x
}
⌉
+
{
x
}
)
⌉
=
2
.
Again,
{
x
}
is always less than 1 but greater than 0 for any irrational number as explained above. So, its value is 0.something.
So,
⌈
(
{
⌈
x
⌉
}
+
⌈
{
x
}
⌉
+
{
x
}
)
⌉
+
{
x
}
= 2.something.
So, ⌈ ( ⌈ ( { ⌈ x ⌉ } + ⌈ { x } ⌉ + { x } ) ⌉ + { x } ) ⌉ = 3 .
So, the answer which we want is the factorial of the above expression which is 3! = 6 .
What I did was plug in pi and derive the answer from there. But there are fancy explanations that tells you why it works above and/or below me!
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The best way to solve this problem is to break x into its components .
Let x = I + f where I is the Integral part of x and f is the fractional part of x such That 0 < f < 1 . Now ,
⌈ x ⌉ = ⌈ I + f ⌉ = I + 1 { x } = { I + f } = f ⌈ { x } ⌉ = ⌈ f ⌉ = 1 { ⌈ x ⌉ } = { I + 1 } = 0 Putting the Values in the expression , we get ⟹ ( ⌈ ( ⌈ ( 0 + 1 + f ) ⌉ + f ) ⌉ ) ! ⟹ ( ⌈ ( ⌈ 1 + f ⌉ + f ) ⌉ ) ! ⟹ ( ⌈ ( 2 + f ) ⌉ ) ! ⟹ ( 3 ) ! = 6