Let A be some subset of a universal set U. The "complement of A" is the set of elements in U that do not belong to A.
For example, if U is the set of all integers {..., -2, -1, 0, 1, 2, ...} and A is the set of all positive integers {1, 2, 3, ...}, then the complement of A is the set {..., -2, -1, 0}.
Notice that the union of A and its complement make up the universal set U.
In this case,
U = {1, 2, 3, 6, 10, 13, 14, 16, 17}
The set {3, 10, 16} is a subset of U, since all three of its elements belong to U.
Then the complement of this set is all the elements of U that aren't in this set:
{1, 2, 6, 13, 14, 17}
They both get their cars washed on every 60th day.
You can solve this equation by finding the lcm (least common multiple):
15 30 45 60 75 90 105
20 40 60 80 100
The lowest common multiple is 60 as it is the first multiple the two have in common.
So, in sixty days, they’ll both get their car washed again
Circumference: 2 * pi * r
pi = 3.14, r = 4
2 * 3.14 * 4 = 25.12
Circumference: 25.12 cm
Area = pi * r^2
pi = 3.14, r = 4
3.14 * 4^2 = 50.24
Area: 50.24 cm^2
