To solve for \( d \), we first need to identify the relationship between the variables given. If the variables \( l \), \( w \), \( h \), and \( x \) are related through a specific formula or equation, please provide that context.
However, if we assume that \( d \) is derived from the dimensions (length \( l \), width \( w \), height \( h \)), we may be looking for a common measurement, like the diagonal of a rectangular prism formed by these dimensions.
The diagonal \( d \) of a rectangular prism can be calculated using the formula:
\[ d = \sqrt{l^2 + w^2 + h^2} \]
Substituting the given values:
- \( l = 30, \text{in} \)
- \( w = 20, \text{in} \)
- \( h = 18, \text{in} \)
Calculating \( d \):
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Calculate \( l^2 \): \[ l^2 = 30^2 = 900 \]
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Calculate \( w^2 \): \[ w^2 = 20^2 = 400 \]
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Calculate \( h^2 \): \[ h^2 = 18^2 = 324 \]
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Now, sum these values: \[ l^2 + w^2 + h^2 = 900 + 400 + 324 = 1624 \]
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Finally, take the square root to find \( d \): \[ d = \sqrt{1624} \approx 40.31 \]
Rounding to the nearest tenth, we find: \[ d \approx 40.3, \text{in} \]
Thus, the rounded value of \( d \) is 40.3 in.