Plain Carbon Steel

If a plain carbon steel test specimen has a tensile strength of 6,000 psi, estimate the Brinell hardness.

Hint
The relationship between hardness and tensile strength is roughly:
$$$TS\:(psi)\simeq 500\:HB$$$
where $$TS$$ is the tensile strength in psi, and $$HB$$ is the Brinell hardness number.
Hint 2
Divide the tensile strength in the problem statement by 500.
For plain carbon steels, the relationship between hardness and tensile strength is roughly:
$$$TS\:(psi)\simeq 500\:HB$$$
where $$TS$$ is the tensile strength in psi, and $$HB$$ is the Brinell hardness number.
$$$HB\simeq \frac{6,000\:psi}{500}\simeq 12$$$
Note the units for HB are in psi or kg/mm^2 (Pascals), but the results are usually reported unitless.
$$$\simeq 12$$$