Question 588607
There's not enough information here to tell where the difficulty was. It could have been a math error. But maybe more important is that you need to remember that in using your method you actually found the volume of the sand plus the volume of the space between the grains of sand.
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Maybe the exercise required that you are only interested in the actual volume of all the grains of sand, meaning that you must not count the space between the irregular shaped grains of sand. If that is the case, then you might want to use the Archimedes principle.
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In times long gone by, Archimedes discovered a means of determining the volume of irregular shaped bodies. It is based on the principle that water and an irregular shaped item cannot both occupy the same space at the same time. When the irregular shaped item is put into water, it will displace a volume of water that is equal to its volume. So here is a way that you might have been expected to solve this problem.
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First partially fill the cylindrical bin with just water, but it must be enough to cover the sand that will be added later. Mark the level of the water in the bin. Then pour the sand into the water and this will cause the level of the water to rise as the sand displaces it. When all the sand has been poured into the bin, mark the new level of the water. The volume of the water between the two marks (its original level and its level after all the sand has been poured into it) is equal to the actual volume of just the grains of sand.
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You could then calculate the volume of the water displaced by finding the circular area of the bin (pi times the square of the radius of the cylinder) and multiplying that by the distance between the two marks. (Be sure to have the radius and the distance between the two marks in the same unit of measure.) And this volume of water would equal the volume of just the grains of sand.
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Or you could pour water from the circular bin (being careful not to pour any sand out) into a container that is calibrated for measuring the volume of liquids. Continue pouring until the water has returned to the level of the first mark you made prior to pouring the sand into it. The calibrated container will then tell you the volume of the displaced water and, again, that volume will be equal to the volume of just the grains of sand.
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Maybe this will help. If it's not what you are looking for, post your question again and maybe another tutor will be able to help you.
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