New length = 1.20L (20% increase)<br>
New width = 0.90W (10% decrease)<br>
New height = (1 + r/100)H<br><br>
New volume factor = 1.20 × 0.90 × (1 + r/100) = 1.08(1 + r/100)<br><br>
Volume decreased by 4%, so new volume = 0.96 × original.<br>
1.08(1 + r/100) = 0.96<br><br>
1 + r/100 = 0.96 ÷ 1.08 = 0.888889...<br>
r/100 = 0.888889... − 1 = −0.111111...<br>
r = −11.11% (to 2 d.p.)<br><br>
Final Answer: −11.11%