<span>The most accurate answer is Sarah's with 8,494.84 cm2. While Kevin's answer is accurate if you're using 3.14 for pi, pi is an infinite number and does not end at the 2 decimals he used.</span>
So you have
8 digits (number available) to form
3 digit numbers (number selected).
Using the formula

where a is the number of available digits, P is the permutation function and c is the number of digits to be selected.
The number of three digit numbers that can be formed =

=
336 <span>
O R</span>By using the formula

where a is the number of available digits and c is the number of digits to be selected.<span>
</span>⇒

<span>
</span>⇒

<span>
</span>⇒ Permutation =
336<span>
</span>
Well, to write the definition of "Perpendicular lines form right angel" using "if and only if". the sentence would become :
<em>
</em><em>Two lines are perpendicular if and only if they form a right angle
</em><em>
</em><em />Hope this helps
Add the total of both groups and divide by the total number in each group
Group X = 535 / 18 = 29.72 mean
group Y = 500 / 18 = 27.78 mean
Group X has the higher mean