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Mathematics

a, b and c are in continued proportion.

Assertion (A): a is first proportion.

Reason (R): The first proportion is always the smallest of the three numbers.

  1. Assertion (A) is true, but Reason (R) is false.

  2. Assertion (A) is false, but Reason (R) is true.

  3. Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct reason for Assertion (A).

  4. Both Assertion (A) and Reason (R) are correct, and Reason (R) is incorrect reason for Assertion (A).

Ratio Proportion

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Answer

Three numbers a, b, c are in continued proportion if:

ab=bc\dfrac{a}{b} = \dfrac{b}{c}

⇒ b2 = ac

Here, a is called the first proportion, b is the mean (or geometric mean), c is the third proportion.

So, assertion (A) is true.

Lets take an example, a = 9, b = 6 and c = 4.

When three numbers a, b, c are in continued proportion if:

ab=bc96=6432=32\Rightarrow \dfrac{a}{b} = \dfrac{b}{c}\\[1em] \Rightarrow \dfrac{9}{6} = \dfrac{6}{4}\\[1em] \Rightarrow\dfrac{3}{2} = \dfrac{3}{2}

Here, a = 9 is first proportion but it is not the smallest number among three.

So, reason (R) is false.

Thus, Assertion (A) is true, but Reason (R) is false.

Hence, option 1 is the correct option.

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