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Sloan [31]
3 years ago
13

Find the area of of a regular octagon with side length 20 cm.

Mathematics
1 answer:
Alla [95]3 years ago
8 0

A=2(1+\sqrt{2})a^2=2·(1+\sqrt{2})·20^2≈1931.37085cm²

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10
sveta [45]

This question was not written properly

Complete Question

Steve has 54 stamps in his collection of 13 cent, 29 cent, and 45 cent stamps, totaling a value of $15.98. If the number of 13 cent stamps is doubled, the new total value of his stamp collection would be $17.80. Find the number of each type of stamp in his collection.

Answer:

a) The number of 13 cent = 14

b) The number of 29 cent = 24

c) The number of 45 cent = 16

Step-by-step explanation:

We are told he has 54 stamps in total.

These stamps are;13 cent, 29 cent, and 45 cent stamps.

Let's

Number of 13 cent = a

Number of 29 cent = b

Number of 45 cent = c

Hence,

a + b + c = 54........... Equation 1

The total value of the 3 stamps are $15.98.

1 cent = $0.01

We have

0.13a + 0.29b + 0.45c= $15.98 ......... Equation 2

We know from the question that:

13 cent stamps is doubled, the new total value of his stamp collection would be $17.80.

Therefore

2(0.13a) + 0.29b + 0.45c = 17.8

0.26a + 0.29b + 0.45c = 17.8 ......... Equation 3

Combining Equation 2 and 3 together

0.13a + 0.29b + 0.45c= 15.98 ......... Equation 2

0.26a + 0.29b + 0.45c = 17.8 ......... Equation 3

We eliminate b and c by Subtracting Equation 3 from 3

0.13a = 1.82

a = 1.82/0.13

a = 14

a + b + c = 54........... Equation 1

Since a = 14

14 + b + c = 54

b + c = 54 - 14

b + c = 40

c = 40 - b

Substitute 40 - b for c and 14 for a is Equation 2

0.13a + 0.29b + 0.45c= 15.98 ......... Equation 2

0.13(14 ) + 0.29b + 0.45(40 - b) = 15.98

= 1.82 + 0.29b + 18 - 0.45b = 15.98

Collect like terms

1.82 + 18 - 15.98 = 0.45b - 0.29b

3.84 = 0.16b

b = 3.84/0.16

b = 24

Hence: Solving for c

a + b + c = 54........... Equation 1

14 + 24 + c = 54

38 + c = 54

c = 54 - 38

c = 16

Therefore,

The number of 13 cent = 14

The number of 29 cent = 24

The number of 45 cent = 16

8 0
3 years ago
One sunflower if 63 inches tall. Another if 4 and 7/8 inches shorter. How tall tall is the second sunflower. I don't know how to
VikaD [51]
Multiply the number to get your product
6 0
3 years ago
Read 2 more answers
Find the surface area of the shape below.
almond37 [142]

Answer:

54m^2

Step-by-step explanation:

Each square has a equal sides, which is 3m

in order to find the surface area, it's

Formula : Base x height = Area

The total surface area would be all the area's added together

3x3=9cm^2

so each square is 9m^2

there are 6 squares so

9+9+9+9+9+9=54m^2

or you can do 9x6=54m^2

8 0
3 years ago
Simplify 2 a + 4 - 7 a + a
AlexFokin [52]
2a + 4 - 7a + a

2a -7a +a +4

-5a + a +4

-4a + 4

-4a + 4 is your answer

hope this helps
8 0
3 years ago
1. Martin can pour a concrete walkway in 6 hours working alone. Victor has
Bond [772]

Answer:

2.4 hr. = time working together

Step-by-step explanation:

Let x = time working together

x/6 = work done by Martin

x/4 = work done by Victor

Martin's part + Victor's part = 1 jog done

x/6 + x/4 = 1  Multiply thru by 12

2x + 3x = 12

5x = 12

x = 2.4 hr.

6 0
3 years ago
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