Question

The mean proportional of the line segments of length 4 cm and 7 cm is ________.(Use geometric method)

• A. 2.5
• B. 4.2
• C. 9.1
• D. 5.3

Answer 1

The correct option is D

5.3

i) Draw a ray AX of length greater than (4 + 7) cm.

ii) Cut off the part AB from AX equal to 7 cm and the part BC from BX equal to 4 cm.

iii) Draw a perpendicular bisector PQ of AC. PQ intersects AC at O.

iv) Draw a semi-circle by taking centre at O and radius equal to OA or OC.

v) Draw a perpendicular on OC at B, which intersects the semi circle at the point D.

vi) Join B and D.

vii) BD is the required mean proportional is equal to 5.3 cm.

Hence, the mean proportional = 5.3 cm.