Nihit wrote:

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The figure above shows the dimensions of a semicircular cross section of a one-way tunnel(dia= 20 ft). The single traffic lane is 12 feet wide and is equidistant from the sides of the tunnel. If vehicles must clear the top of the tunnel by at least ½ foot when they are inside the traffic lane, what should be the limit on the height of vehicles that are allowed to use the tunnel?

A. 5½ ft

B. 7½ ft

C. 8 ½ ft

D. 9½ ft

E. 10 ft

radius =10

Say AOB is base of the semi circle.

points X and Y are on edges of the traffic lane (XY=12)

OX=6

Find the height perpendicular to X and touches the semi circle.

= sqrt (6^2+10^2) =8

we need 1/2 ft clearance.

so height must be (8-1/2) =71/2 ft

B.

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