Estimating Hardness

If a plain carbon steel test specimen has a tensile strength of 50 MPa, estimate the Brinell hardness.

Hint
The relationship between hardness and tensile strength is roughly:
$$$TS\:(MPa)\simeq 3.5\:HB$$$
where $$TS$$ is the tensile strength in MPa, and $$HB$$ is the Brinell hardness number.
Hint 2
Divide the tensile strength in the problem statement by 3.5.
For plain carbon steels, the relationship between hardness and tensile strength is roughly:
$$$TS\:(MPa)\simeq 3.5\:HB$$$
where $$TS$$ is the tensile strength in MPa, and $$HB$$ is the Brinell hardness number.
$$$HB\simeq \frac{50\:MPa}{3.5}\simeq 14.3$$$
Note the units for HB are in psi or kg/mm^2 (Pascals), but the results are usually reported unitless.
$$$\simeq 14.3$$$