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The areas of three adjacent faces of a solid cuboid are 66┬аcm2, 192┬аcm2 and 198┬аcm2. What is the volume (in cm3) of the cuboid?
1594
1584
1792
1782
1584
Multiply the three areas and take the square root. Since 66=6├Ч11, 192=3├Ч64, and 198=18├Ч11, the product is (6├Ч11)├Ч(3├Ч64)├Ч(18├Ч11)=(6├Ч3├Ч18)├Ч(112)├Ч64=324├Ч121├Ч64. Taking the square root gives 18├Ч11├Ч8=1584.
Areas of three adjacent faces of a cuboid are A1тАЛ=66┬аcm2, A2тАЛ=192┬аcm2, and A3тАЛ=198┬аcm2.
V=A1тАЛ├ЧA2тАЛ├ЧA3тАЛтАЛ
Multiply the three areas and take the square root. Since 66=6├Ч11, 192=3├Ч64, and 198=18├Ч11, the product is (6├Ч11)├Ч(3├Ч64)├Ч(18├Ч11)=(6├Ч3├Ч18)├Ч(112)├Ч64=324├Ч121├Ч64. Taking the square root gives 18├Ч11├Ч8=1584.
Students often try to solve for l,w,h individually by setting up equations like lw=66, wh=192, lh=198, which is more time-consuming than using the direct product formula.
Define face area relations
Let the dimensions of the cuboid be length l, width w, and height h. The areas of adjacent faces are lw=66, wh=192, and lh=198.
lw=66,wh=192,lh=198
Multiply equations
Multiplying the three equations gives (lw)(wh)(lh)=66├Ч192├Ч198. This simplifies to (lwh)2=2509056.
(lwh)2=2509056
Calculate Volume
The volume V=lwh is the square root of the product of the areas. Calculate V=2509056тАЛ=1584.
V=66├Ч192├Ч198тАЛ=1584
B is correct because the volume of the cuboid is calculated as the square root of the product of its adjacent face areas: 66├Ч192├Ч198тАЛ=1584┬аcm3.
This concept is similar to finding the product of roots in quadratic equations or geometric mean problems in statistics.