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3 years ago

What is the exact circumference of the circle?

1 answer:

7 0

Data:

Formula: diameter = 2*radius

Formula: (Circle length)
 $C = 2* \pi *r$

Solving: Using the data
diameter = 2*radius
20 = 2*r
2r = 20
$r = \frac{20}{2}$
$\boxed{r = 10\:ft}$

Now, replace in the circumference length formula
 $C = 2 \pi *r$
$C = 2 \pi *10$
$\boxed{\boxed{C = 20 \pi \:ft}}\end{array}}\qquad\quad\checkmark$

Answer:
The exact circumference of the circle is $20 \pi \:ft$

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Murrr4er [49]

Answer:

405

Step-by-step explanation:

So he built 5/9 of the wall, than added the extra 180 bricks to finish the wall.

so 5/9 + 180 = 9/9

so 180 = 4/9 Because 5/9 + 4/9 = 9/9

So to figure out how many bricks are in the wall we want to know what 1/9 of bricks equals and to work this out we need to divide 180 by 4

which equals 45.

Now we know that 1/9 = 45

so now to figure out what 9/9 is just multiply 45 by 9 which equals 405

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3 years ago

A man travels 20 km by car from Town P to Town Q at an average speed of x km/h. He finds that the time of the journey would be s

yuradex [85]

Answer:

x = 20.

Step-by-step explanation:

First, you should remember the relation:

Distance = Speed*Time.

First, we know that a man travels a distance of 20km at a speed of x km/h, in a time T.

We can write this as:

20km = (x km/h)*T

We know that the time is shortened by 12 minutes if the speed is increased by 5km/h

Rewriting these 12 minutes in hours (remember that 60min = 1 hour)

12 min = (12/60) hours = 0.2 hours

Then from this, he can travel the same distance of 20km in a time T minus 0.2 hours if the speed is increased by 5 km/h

We can write this as:

20km = (x + 5 km/h)*(T - 0.2 h)

Then we have a system of two equations, and we want to find the value of x:

20km = (x km/h)*T

20km = (x + 5 km/h)*(T - 0.2 h)

First, we should isolate the variable T in one of the equations, if we isolate it in the first one, we will get:

20km/(x km/h) = T

Replacing that in the other equation we get:

20km = (x + 5 km/h)*(T - 0.2 h)

20km = (x + 5 km/h)*( 20km/(x km/h) - 0.2 h)

Now we can solve this for x.

Removing the units (that we know that are correct) so the math is easier to read, we get:

20 = (x + 5)*(20/x - 0.2)

We only want to solve this for x.

20 = x*20/x - x*0.2 + 5*20/x - 5*0.2

20 = 20 - 0.2*x + 100/x - 1

subtracting 20 in both sides we get:

20 - 20 = 20 - 0.2*x + 100/x - 1 - 20

0 = -0.2*x + 100/x - 1

If we multiply both sides by x we get:

0 = -0.2*x^2 + 100 - x

-0.2*x^2 - x + 100 = 0

This is just a quadratic equation, we can solve it using the Bhaskara's equation, the solutions are:

$x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4*(-0.2)*100} }{2*-0.2} = \frac{1 \pm 9 }{-0.4}$

Then the two solutions are:

x = (1 + 9)/-0.4 = -25

x = (1 - 9)/-0.4 = 20

As x is used to represent a speed, the negative solution does not make sense, so we should use the positive one.

x = 20

then the average speed initially is 20 km/h

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2 years ago