The first three terms of a proportion are $15, 20 a n d 30$ . Find the fourth term.

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Solution

Finding the fourth term of the given proportion:
Let the fourth term of the given proportion is $X$
As we have the first three terms of a proportion are $15, 20 a n d 30$
so, we can write it as $15 : 20 : : 30 : X$
Now, we know that when the two ratios form proportion then the given ratios are equal.
Using that we have,
$\Rightarrow \frac{15}{20} = \frac{30}{X} \Rightarrow X = \frac{30 \times 20}{15} (C r o s s - M u l t i p l i c a t i o n) \Rightarrow X = \frac{600}{15} \Rightarrow X = 40$
Hence, the fourth term of the given proportion is $40$ .

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