The thermal conductivity of brick is `1.7 W m^(-1) K^(-1)`, and that of cement is `2.9 W m^(-1) K^(-1)`.What thickness of cement will have same insulation as the brick of thickness `20 cm`.

Explanation

To find the thickness of cement that will provide the same insulation as a brick of thickness 20 cm, we can use the relationship between thermal conductivity and thickness. The formula we will use is based on the principle that for the same insulation, the ratio of thermal conductivity to thickness must be equal for both materials.

### Step-by-Step Solution:

1. **Identify the given values:**
- Thermal conductivity of brick, \( k_1 = 1.7 \, \text{W m}^{-1} \text{K}^{-1} \)
- Thickness of brick, \( L_1 = 20 \, \text{cm} = 0.2 \, \text{m} \) (convert cm to m)
- Thermal conductivity of cement, \( k_2 = 2.9 \, \text{W m}^{-1} \text{K}^{-1} \)
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