A substance has density 78.4 lb/ft^3, with water density 62.4. What is its approximate SG?

A substance has density 78.4 lb/ft^3, with water density 62.4. What is its approximate SG?

• A. 1.23
• B. 1.20
• C. 1.28
• D. 1.26

Answer: (D)

Specific gravity is the ratio of a substance’s density to the density of water: SG = ρ_sub / ρ_water. With ρ_sub = 78.4 lb/ft^3 and ρ_water = 62.4 lb/ft^3, SG = 78.4 / 62.4 ≈ 1.256, which rounds to about 1.26. This means the substance is roughly 26% denser than water. The other numbers are farther from the exact ratio (e.g., 1.23, 1.28, or 1.20 would correspond to densities not matching 78.4 lb/ft^3).

Specific gravity is the ratio of a substance’s density to the density of water: SG = ρ_sub / ρ_water. With ρ_sub = 78.4 lb/ft^3 and ρ_water = 62.4 lb/ft^3, SG = 78.4 / 62.4 ≈ 1.256, which rounds to about 1.26. This means the substance is roughly 26% denser than water. The other numbers are farther from the exact ratio (e.g., 1.23, 1.28, or 1.20 would correspond to densities not matching 78.4 lb/ft^3).