Answer:
number (c)
Step-by-step explanation:
I am not sure about this
The circumference of every circle is (pi) times (diameter).
The diameter is (2 x radius), so we can write
Circumference = (pi) x (2 x radius) .
The question gives us the circumference, and the number to use for (pi).
I shall now pluggum in:
(31.4 cm) = (3.14) x (2 x radius)
Divide each side by 3.14: (31.4 cm)/(3.14) = 2 x radius
Divide each side by 2 : (31.4 cm) / (2 x 3.14) = radius
5 cm = radius
So we can start with the full of possibilities and eliminate them one by one.
The full set is {0,1,2,3,4,5,6,7,8,9}.
Now we know that any prime greater than 2 is odd as otherwise it would have 2 as a factor, so we can eliminate all of these digits that would be an even number, leaving:
{1,3,5,7,9}
We also know that any prime greater than 5 cannot be a multiple of 5 and that all numbers with 5 in the digits are a multiple of 5, so we can eliminate 5.
{1,3,7,9}
We know that 11,13,17 and 19 are all primes, so we cannot eliminate any more of these, leaving the set:
{1,3,7,9} as our answer.
