The volume of a square pyramid is (1/3)(area of base)(height of pyramid).
Here the area of the base is (10 ft)^2 = 100 ft^2.
13 ft is the height of one of the triangular sides, but not the height of the pyramid. To find the latter, draw another triangle whose upper vertex is connected to the middle of one of the four equal sides of the base by a diagonal of length 13 ft. That "middle" is 5 units straight down from the upper vertex. Thus, you have a triangle with known hypotenuse (13 ft) and known opposite side 5 feet (half of 10 ft). What is the height of the pyramid?
To find this, use the Pyth. Thm.: (5 ft)^2 + y^2 = (13 ft)^2. y = 12 ft.
Then the vol. of the pyramid is (1/3)(area of base)(height of pyramid) =
(1/3)(100 ft^2)(12 ft) = 400 ft^3 (answer)
Answer:
u = (-21)/20
Step-by-step explanation:
Solve for u:
u + 1/4 = (-4)/5
Put each term in u + 1/4 over the common denominator 4: u + 1/4 = (4 u)/4 + 1/4:
(4 u)/4 + 1/4 = -4/5
(4 u)/4 + 1/4 = (4 u + 1)/4:
1/4 (4 u + 1) = -4/5
Multiply both sides of (4 u + 1)/4 = (-4)/5 by 4:
(4 (4 u + 1))/4 = (-4)/5×4
4×(-4)/5 = (4 (-4))/5:
(4 (4 u + 1))/4 = (-4×4)/5
(4 (4 u + 1))/4 = 4/4×(4 u + 1) = 4 u + 1:
4 u + 1 = (-4×4)/5
4 (-4) = -16:
4 u + 1 = (-16)/5
Subtract 1 from both sides:
4 u + (1 - 1) = (-16)/5 - 1
1 - 1 = 0:
4 u = (-16)/5 - 1
Put (-16)/5 - 1 over the common denominator 5. (-16)/5 - 1 = (-16)/5 - 5/5:
4 u = (-16)/5 - 5/5
-16/5 - 5/5 = (-16 - 5)/5:
4 u = (-16 - 5)/5
-16 - 5 = -21:
4 u = (-21)/5
Divide both sides by 4:
u = ((-21)/4)/5
5×4 = 20:
Answer: u = (-21)/20
Sales increased 50% last year, from $5,000 to $10,000. When sales dropped from $10,000 to $5,000 this year, sales decreased 50%
Let x represent the shorter sides, then 2x + 1 would represent the longer sides. There are four short sides and two long sides. The perimeter is 162 cm. The equation: 4x + 2(2x + 1) = 162 4x + 8x + 2 = 162 8x + 2 = 162 Subtract 2 from both sides. 8x = 160 Divide both sides by 8. x = 20 The shorter sides are 20 cm in length. The longer sides are 2x + 1, or 41 cm in length. Check: 4 * 20 + 2 * 41 = 162 80 + 82 = 162 162 = 162, values check.
