D. 1/4
Explanation:
a perfect square is written in the form
(1)
In our problem, we have this perfect square:
(2)
with C being unknown. However, by comparing (1) and (2), we know that

So, we find

and therefore, the missing term must be

so the complete square is

Answer: 4 or 
To find the square root of a number, remember that there will be two factors that are the same that will give you the product.
Lets start from 1:
1 x 1 = 1
2 x 2 = 4
3 x 3 = 9
4 x 4 = 16
As you can see, 4 x 4 is 16. To make sure I'm correct, remember that a square roots consists two identical factors.
4 and 4 are the same numbers.
Therefore,
= 4
It can also be written as 
Answer:
31465 ways
Step-by-step explanation:
Given data
Let us apply the combination formula
nCr = n! / r! * (n - r)!
n= 31
r= 4
substitute
= 31!/4!(31-4)!
= 31!/4!(27)!
= 31*30*29*28*27!/ 4!(27)!
= 31*30*29*28/4!
=31*30*29*28/4*3*2*1
=755160/24
=31465 ways
Hence there are 31465 possible ways to rank it
49 divided by 3 = 16.33
Each sibling has about 16 rare coins.
Circumference of circular path=pi*d^2/4
=44.156
length of light=1.45
light needed=44.156/1.45
=31 approx