The distance from the center of a pentagon to one of it vertices is called the circumradius (R).
The distance from the center of a pentagon to the midpoint of one of its sides is called the inradius (r).
R = circumradius
r = inradius
A = area
a = side length
Memorize the following formulas:
R = (1/10)a * sqrt[50 + 10 * sqrt(5)]
r = (1/10)a * sqrt[25 + 10 * sqrt(5)]
A = (1/4)a^2 * sqrt[25 + 10 * sqrt(5)]
How do we find the length of a side from the area....that's the hard part...
beccaa wrote:my friend got 681
your friend didn't round up. it's 682
So are we going with 682?
no its 681
the decimal after the 1 is LOWER than .5 so you do not round up
What does it come to WITHOUT the rounding?
beccaa wrote:no its 681
the decimal after the 1 is LOWER than .5 so you do not round up
no, it's not. it's 681.7. Round up to 682
HotHeather wrote:beccaa wrote:no its 681
the decimal after the 1 is LOWER than .5 so you do not round up
no, it's not. it's 681.7. Round up to 682
no its 681.4.
you must have rounded at another step
beccaa wrote:HotHeather wrote:beccaa wrote:no its 681
the decimal after the 1 is LOWER than .5 so you do not round up
no, it's not. it's 681.7. Round up to 682
no its 681.4.
you must have rounded at another step
you're wrong. I'm going to take a bath
oooohtone wrote:*so confused*
a bath .. it's when you get naked and wash your body
its says to round up to the nearest whole number, not round up if applicable....
I don't think the PROPER way to round matters. From the puzzle page:
"What is the area of the green part, in square centimetres? Please round up to the nearest whole number, and submit only the answer."
I put 682, hope that's right.
I've got side length of the pentagon as 21.5665 cm.
And the angles of a pentagon are all 108... so the angle of the triangle is 82 degrees.
From here.. it's trig.. and I don't know what to do. Anyone else?
thnx!!!I ut 682(I'm not good at the math ones...)
i triple check and i got 682 all 3 times so itis 682
