Question

Find the fourth proportional to 7 , 12 and 21​

Answer 1

Answer:

36

Step-by-step explanation:

Answer: Let the fourth proportional to the numbers 7, 12, and 21 be x. Then from the definition of the fourth proportional, we must have:

7: 12 :: 21: x or in terms of the fractions we can write;

7x = 12 × 21. In other words, we have x = {12 × 21}/7 = 27.

Answer 2

SOLUTION

TO DETERMINE

The fourth proportional to 7 , 12 and 21

EVALUATION

Let x be the fourth proportional to 7 , 12 and 21

So by the given condition

7 : 12 = 21 : x

$\displaystyle \sf{ \implies \frac{7}{12} = \frac{21}{x} }$

$\displaystyle \sf{ \implies 7x = 12 \times 21 }$

$\displaystyle \sf{ \implies x = \frac{12 \times 21}{7} }$

$\displaystyle \sf{ \implies x = 12 \times 3 }$

$\displaystyle \sf{ \implies x = 36 }$

FINAL ANSWER

Hence the fourth proportional to 7 , 12 and 21 is 36

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