1. A box contains a mixture of small copper spheres and small lead spheres. The
ID: 626814 • Letter: 1
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1. A box contains a mixture of small copper spheres and small lead spheres. The total volume of both metals is measured by the displacement of water to be 430 cm3 and the total mass is 4.33kg . What percentage of the spheres are copper? x+y=4330. x/8.94+y/11.34=430 4330-y/8.94+y/11.34=430 Plug in, y=4330-x answer should be y=2.295 kg, x=2.035 So, 2.035/4.33*100=47% My answer is 47.%. However, it is wrong. I have no idea what is wrong with it. 2. The smallest number of packages of buns and hot dogs you need, respectively is 5,4 respectively. The question is: For this picnic, you need to feed at least 700 people. If you want to feed everyone, but still have equal numbers of buns and hot dogs, what is the minimum number of packages of buns and hot dogs you need, respectively? Express your answer as two integers separated by a comma. 2-1. For another picnic, you want to make hamburgers with pickles, again without having any left over. You need to balance the number of packages of buns (which usually contain 8 buns) with the number of packages of hamburger patties (which usually contain 12 patties) and the number of jars of pickles (which contain 18 slices). Assume that each hamburger needs three pickle slices. What is the smallest number of packages of buns, packages of patties, and jars of pickles, respectively? Express your answer as three integers separated by commas. 3. Which is x/(yz) same equivalent expression? a. xy/z b. x/yz c. xz/yExplanation / Answer
FOLLOW THIS You need the densities of the metals density copper = 8.94g/cm^3 density lead = 11.34 g/cm^3 density = mass / volume mass = density x volume Now, we can write expressions for the mass of Cu and Pb using the density Let volume copper = A mass copper = density x volume = 8.94 g/cm^3 x A = 8.94A Let Volume Lead = B mass lead = density x volume = 11.34 g/cm^3 x B = 11.34 B We know that the total mass of the two metals is 4250 g 4250 g = mass copper + mass lead So, using our two expressions 4250 = 8.94A + 11.34 B Now, we also know the total volume Total volume = A + B = 412 cm^3 Thus B = 412 - A substitute this expression for B into the mass equation and solve for A 4250 = 8.94A + 11.34 B 4250 = 8.94A + 11.34 (412 - A) 4250 = 8.94 A + 4672.08 - 11.34A 4250 - 4672.08 = 8.94A - 11.34 A -422.08 = -2.4A A = -422.08 / -2.4 A = 175.87 Volume of Copper = 175.87 cm^3 % copper = volume copper / total volume metal x 100/1 = 175.87 cm^3 / 412 cm^3 x 100/1 = 42.7 %
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