A titanium alloy has a tensile strength of 950 MPa and a density of 4.43 g/cm³, and a high-strength steel has a tensile strength of 1200 MPa and a density of 7.85 g/cm³. About how many times the specific strength (tensile strength/density) of the steel is that of the titanium alloy?

Answer: B. About 1.4 times

The specific strength is 950/4.43 ≈ 214 kN·m/kg for the titanium alloy and 1200/7.85 ≈ 153 kN·m/kg for the steel, so the ratio is 214/153 ≈ 1.40, about 1.4 times (MPa divided by g/cm³ becomes kN·m/kg once units are made consistent). About 0.79 times compares only the tensile strengths (950/1200), ignoring weight. About 1.8 times takes only the density ratio (7.85/4.43 ≈ 1.77), ignoring the difference in strength. For a member carrying the same load, a higher specific strength allows a lighter design, which is why aircraft structures use titanium alloys, aluminum alloys and carbon-fiber composites. Material cost and ease of fabrication must also be weighed in the choice, however.