Numerical problem III — task. Science State Board, Class 7.

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Two spheres of same size are made from copper and iron respectively. Find the ratio between their masses. Density of copper \(8,900\) \(kg/m^3\) and iron \(7,800\) \(kg/m^3\).

[NOTE: Enter the answer up to two decimal places.]

Density of copper and iron is denoted as \(D_c\) and \(D_i\), respectively.

Ratio of masses of copper (\(M_c\)) and iron (\(M_i\)):

The formula for density is

\(\text{Density} = \frac {\text{Mass}} {\text{Area}}\)
\(\text{Density} = \frac {\text{Mass}} {\text{Volume}}\)
\(\text{Density} = \frac {\text{Volume}} {\text{Mass}}\)

From the above formula, the mass of an object is

\begin{array}{l} Mass = i \times i \\ = i i \times i i \end{array}

The ratio of masses of copper (\(M_c\)) and iron (\(M_i\)) is

i : i

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24. Numerical problem III

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