The volume of one cloud, in cubic kilometers, grows according to the expression 4^3x – 1, where x is time in hours. Another cloud grows according to the expression 8x. After how many hours will the two clouds have the same volume? What is their volume, in cubic kilometers?

Respuesta :

Answer:

x = ⅔ hr

V = 4 km³

Step-by-step explanation:

The volume of the first cloud is given as:

V1 = 4^(3x - 1)

The volume of the second cloud is given as:

V2 = 8^x

When the two clouds have the same volume, V1 = V2:

=> 4^(3x - 1) = 8^x

We can rewrite this as:

2^[2(3x - 1)] = 2^[3(x)]

=> 2^(6x - 2) = 2^(3x)

According to the law of indices, we can equate the powers because their bases are equal (2 is the base).

=> 6x - 2 = 3x

6x - 3x = 2

3x = 2

x = ⅔ hr

Hence, after 2/3 hr, their volumes will be equal.

To find the volume after 2/3 hr, we can use the equation of either cloud but let us use the equation for the second cloud for simplicity sake:

V2 = 8^(⅔)

V2 = 4 km³ or 4 cubic kilometers

The clouds will have the same volume of 2.8 square kilometers after 0.35 hours.

When the clouds will have the same volume?

The clouds will have the same volume when:

4^(3x - 1) = 8x

Where these two are the expressions for the volumes of each cloud.

Notice that in the left side we have an exponential equation while on the right side we have a linear one, so we can't solve this analytically in a direct way.

What we can do is graph both curves and see when they intersect, like in the graph below:

There we can see that the curves intersect at x = 0.35.

The volume of the clouds at that time will be:

y = 8*0.35 = 2.8 square kilometers.

If you want to learn more about volume, you can read:

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