The ends of a segment located on one side of a straight line are at a distance of 3 cm and 9 cm

The ends of a segment located on one side of a straight line are at a distance of 3 cm and 9 cm from it. At what distance from this straight line is the middle of this segment.

Consider a quadrilateral ABCD.

AB and CD are perpendicular to the same line AD. If two lines are perpendicular to the third line, then these two lines are parallel.

Therefore AB // CD. In the same way, one can prove that AB // CD // MN

Hence the quadrilateral ABCD is a rectangular trapezoid.

MN is its middle line, since M is the middle of BC and MN // AB // CD.

The middle line of the trapezoid is equal to half the sum of the bases.

MN = (AB + CD) / 2 = (3 + 9) / 2 = 6 cm.

Answer. 6 cm.



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