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Question
Find the third proportional to `5(1)/(4) and 7.`
Solution
Let x be the third proportional to `5(1)/(4) and 7`
then `5(1)/(4) : 7 : : 7 : x`
⇒ `(21)/(7) : 7 : : 7 : x`
∴ `(21)/(4) xx x` = 7 x 7
x = `(7 xx 7 xx 4)/(21)`
= `(28)/(3)`
= `9(1)/(3)`
∴ Third proportional = `9(1)/(3)`.
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