Question 1

Paper 1Hard15 marks

A council is planning a radio relay, HH for three flood-monitoring stations, AA BB and CC The relay is to be placed so that it is the same distance from each station. Figure 1 is a coordinate map; coordinates are in kilometres, with east as the positive xx-direction and north as the positive yy-direction.

The equation of the line segment ABAB is y=13x+53y=\frac13x+\frac53 and its midpoint is M(4,3)M(4,3)

0123456780123456789east (km)north (km)ABCM
(a)

Write down the coordinates of stations AA and CC from Figure 1.

[2]
(b)

Show that the equation of the perpendicular bisector of ABAB is y=−3x+15y=-3x+15

[3]
(c)

Use your answer to part (b) and the information in Figure 1 to find the coordinates of a point that is the same distance from all three stations. Show enough working to justify that it has this property.

[7]
(d)

The relay can serve the stations only if it is no farther than 3.6 km3.6\text{ km} from each station. Determine whether the point you found in part (c) meets this requirement. Give the distance to three significant figures.

[3]

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