Answer:
- <u>First choice, 984 cm²</u>
Explanation:
The plastic pencil case has form of a triangular prism.
This triangular prism has five faces:
- Top and bottom faces: two congruent triangles with a 10 cm base and 12 cm height.
- Lateral faces: two congruent rectangles with a 24 cm length and 13 cm widht, and one rectangle with 24 cm length and 10 cm widht.
<u>Surface area:</u>
- <u>Top and bottom triangles</u>:
area = (1/2) base × height
area of one triangle = 10 cm × 12 cm × (1/2) = 60 cm²
area of the two triangles = 2 × 60 cm² = 120 cm²
- <u>Lateral rectangles:</u>
area of a rectangle = length × width
area of the trhee triangles = 24 cm × 10 cm + 2 × 24 cm × 13 cm = 240 cm² + 624 cm² = 864 cm².
- <u>Total area: </u>120 cm² + 864 cm² = 984 cm²
Answer: first choice, 984 cm²
Answer: 16 cm^2.
Step-by-step explanation: The volume of a pyramid is equal to one-third the product of the area of the base and the height:
In this case, the base is a square, so its area is:
A=L^2 where "L" is the lenght of the base edge
So the volume would be:
V=16*3/3
Answer:
a = 3, b = -1, c = 10
Step-by-step explanation:
Let the three numbers be a, b and c.
Equation 1: a + b + c = 12
Equation 2: a + 2b + 3c = 31
Equation 3: 9b + c = 1
Equation 2 - Equation 1:
Equation 4: b + 2c = 19
Equation 3 times by the number 2
Equation 5: 18b + 2c = 2
Equation 5 - Equation 4
17b = -17
b = -1
Substitute into Equation 4:
2c - 1 = 19
2c = 20
c = 10
Substitute into Equation 1:
a + b + c = 12
a - 1 + 10 = 12
a = 3
