A homeowner wants some insulation blown into her attic. The original quote was for 16 cm of R-17 rated insulation. If she wants the attic insulated to R-44, what thickness (in cm) does she need to use

the value of the required thickness is 41.4 cm

Explanation:

Given that;

R1 = 17

R2 = 44

L1 = 16

L2 = ?  

we know that, from thermal conductivity formula

P = 1 / R

P = k / L  

1 / R = k / L    

since k of a distinct material  is constant,

we can take

L / R = constant

L1 / R1 = L2 / R2  

L1R2 = L2R1

L2 = (L1 × R2) / R1  

so we substitute

L2 = (16 × 44) / 17

L2 = 704 / 17

L2 = 41.4 cm  

Therefore the value of the required thickness is 41.4 cm  

the answer is 12 as i may remember

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