Answer:
0.14 lb . . . closest choice is 0.11 lb
Step-by-step explanation:
The inside and outside radii are 1/8 in and 3/8 in, respectively. Then the area of the top of the washer is ...
A = π(R² -r²) = π((3/8)² -(1/8)²) = π(9/64 -1/64) = π/8 . . . square inches
The height of the stack of 5 washers will be 5×(1/4 in) = 5/4 in. So, the volume of material in the stack of washers is ...
V = Bh = (π/8)(5/4) = 5π/32 . . . cubic inches
The weight of material is the product of volume and density, so is ...
W = (5π/32 in³)(0.285 lb/in³) ≈ 0.1399 lb ≈ 0.14 lb
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<em>Comment on the question</em>
Since this answer does not correspond to any of the offered choices, we suggest you ask your teacher to work this out for you. We suspect they will have difficulty justifying any of the answer choices shown here. (0.11 lb corresponds to 4 washers, not 5.)
The perimeter of RSTU can be calculated alone without the help of MNPQ. It would be just 2(4) + 2(3) = 14 units. However, it would be much sensible if you want to find the parameter of the bigger rectangle. Since they are similar, you could use ratio and proportion.
(length/width)∨MNPQ = (length/width)∨RSTU
(x/9) = (3/4)
x = 6.75 units
Thus the perimeter of MNPQ is 2(6.75) + 2(9) = 31.5 units
the answer is 30 to 18 is 60%
