Question 57

The third proportional of two numbers 9 and 15 is

Solution

Three numbers a,b,c are in proportion iff $$b^2 = ac$$ where $$b$$ is the mean proportion and $$c$$ is the third proportion

The given numbers are 9 and 15

=> $$(15)^2 = 9 \times c$$

=> $$c = \frac{15 \times 15}{9}$$

=> $$c = 5 \times 5 = 25$$

=> Ans - (C)

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