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Last weekend Ali visited an aviation festival near his neighborhood. In an experiment at the festival, an engineer introduced the element rhenium, which is used to make jet engine parts. The engineer showed the onlookers a small pyramid-shaped part of the element. The part was obtained by cutting one corner of a cube with edges of length 6 centimeters as shown.
What is the density of rhenium?Ali wonders.
Substitute values
LHS⋅5=RHS⋅5
Rearrange equation
Use a calculator
Round to nearest integer
As the diagram indicates, the base of the hollow part is a square with a side length of 5 centimeters. Additionally, the mold is a cube with an edge length of 7 centimeters. Therefore, the hollow is a square prism with a base edge length of 5 centimeters and height of 7 centimeters.
The volume of this square prism can be calculated as the product of its base area and its height. Since the base of the prism is a square with a side length of 5 centimeters, the base area is 52 square centimeters. The volume of the hollow is 175cm3.After discussing hexagonal cells of beehives, Diego thinks he can approximate the number of cells in his body. His teacher recommends for Diego to treat a cell like a sphere with a diameter of 2×10-3 centimeters.
If Diego's weight is 60 kilograms and the density of a cell is approximately the density of water, which is 1 gram per cubic centimeter, help Diego approximate the number of cells in his body. Write the answer in scientific notation.
About 1.4×1013 cells
The formula for the volume of a sphere is V=34πr3, where r is the radius of the sphere.
r=10-3
(am)n=am⋅n
ca⋅b=ca⋅b
Use a calculator
Round to 1 decimal place(s)
Rewrite (4.2)(10-9) as 4.2×10-9
M=60000g, m=4.2×10-9g
Cross out common factors
Simplify quotient
Write as a product of fractions
am1=a-m
Calculate quotient
Multiply
\RoundSigDig{2}
Write in scientific notation
Throughout the lesson, different cases involving concepts of density based on area and volume have been discussed. Considering these situations, the challenge presented at the beginning of the lesson can be solved.
Ali knows that the small pyramid-shaped part of the element was obtained by cutting one corner of a cube with edges of length 6 centimeters.
The volume of a pyramid is one-third of the product of its base area and height.