Natural numbers are closed under division: false.
A set is closed under a certain operation if the results of that operation are always inside that set.
So, if natural numbers were closed under division, the division of two natural numbers would always be a natural number.
You have plenty of counterexamples, to pick one you may divide any odd number by 2: 5/2 is not a natural number.
Negative numbers are closed under addition: true.
Let
be two positive numbers. So,
are two negative numbers. Their sum is

And since
is positive, we deduce that
is negative, so the sum of two negative numbers is still negative.
Prime numbers are closed under subtraction: false.
This would mean that the subtraction of two primes is also a prime. Again, there are many counterexamples: 7 is prime and so is 3, but their difference 7-3 is 4, which is not prime.
Answer: true
Step-by-step explanation: first you divide its circumference by pi, which you then get 17.990. Round it to 18. Then use the diameter (18) and divide it by 2. You get 9.
Answer:
71 cents
Step-by-step explanation:
Answer:(a) n=0.233
Step-by-step explanation:
Given
We Know according to Taylor tool life

V=cutting speed
T=tool life
n=tool life exponent
c=constant



taking log both side

n=0.233