Question

Find the fourth proportional to 5 7 and 8

Answer 1

The fourth proportional to 5 , 7 and 8 is 11.2

Given :

The numbers 5 , 7 and 8

To find :

The fourth proportional to 5 , 7 and 8

Solution :

Step 1 of 2 :

Form the equation to find the number

Let x be the fourth proportional to 5 , 7 and 8

Then by the given condition

5 : 7 = 8 : x

Step 2 of 2 :

Find the number

Find the value of x

$\displaystyle \sf{ 5 : 7 = 8 : x }$

$\displaystyle \sf{ \implies \frac{5}{7} = \frac{8}{x} }$

$\displaystyle \sf{ \implies 5x = 7 \times 8}$

$\displaystyle \sf{ \implies x = \frac{7 \times 8}{5} }$

$\displaystyle \sf{ \implies x = \frac{56}{5} }$

$\displaystyle \sf{ \implies x = 11.2 }$

Hence the fourth proportional to 5 , 7 and 8 is 11.2

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Answer 2

Answer:

The correct answer of this question is 11.2

Step-by-step explanation:

Given - The fourth proportional to 5 7 and 8.

To Find - Find the fourth proportional to 5 7 and 8.

If the ratio is a:b:: c:d, or a:b = c: d, then the number 'd' is the fourth proportional to a, b, and c.

Let $x$  be the fourth proportional to $5 , 7 , 8$

According to the question,

The given conditions are - 5 : 7 = 8 : x

Now,

Find the value of x

5 : 7 = 8 : x

$\frac{5}{7} = \frac{8}{x} \\5x = 7 . 8$

$x = \frac{7 . 8 }{5}$

$x = \frac{56}{5} \\x = 11.2$

Hence,  the fourth proportional to 5 , 7 and 8 is 11.2

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