The weight of an aluminum product is 15 N in air, and 9.5 N in water. Determine the density of aluminum.

P1 = 15 N.
P2 = 9.5 N.
ρw = 1000 kg / m ^ 3.
ρа -?
ρа = m / V, the density of a substance ρа is the ratio of body mass m to its volume V.
P1 = m * g.
m = P1 / g.
On a body lowered into the water, there are two forces of gravity m * g vertically down and the force of Archimedes vertically up Farkh.
The body weight will be determined by the formula: P2 = m * g – Farch.
P2 = P1 – Farch.
Farch = ρw * g * V.
P2 = Р1 – ρв * g * V.
V = (P1 – P2) / ρw * g.
ρа = (Р1 / g) / ((P1 – Р2) / ρв * g)) = Р1 * ρв / (P1 – Р2).
ρа = 15 N * 1000 kg / m ^ 3 / (15 N – 9.5 N) = 2727 kg / m ^ 3.
Answer: the density of aluminum is ρа = 2727 kg / m ^ 3.