Correct Answer - Option 2 : 6.4
Given:
The numbers for mean proportional = 5.6, and 1.4
The numbers for third proportional = 7 and 4
Concept:
If the mean proportional of a and c is b then the relation between a, b, and c
b2 = (a × b)
If x is the third proportional of a and b then
\({a \over b}= {b \over x}\)
Calculation:
Let us assume the third proportional of 7 and 4, be X then
⇒ \({7 \over 4} = {4 \over X}\)
⇒ X = (4 × 4)/7 = 16/7
⇒ The mean proportional of 5.6 and 1.4 be Y then,
⇒ Y2 = (5.6 × 1.4) = 7.84
⇒ Y = √(7.84) = 2.8
The required product = X × Y
⇒ (2.8) × (16/7) = 0.4 × 16 = 6.4
∴ The required result will be 6.4.
