The length of a ladder is exactly equal to the height of the wall it is learning against. If lower end of the ladder is kept on a stool of height 3 m and the stool is kept 9 m away from the wall, the upper end of the ladder coincides with the top of the wall. Then the height of the wall is
Explanation:
The figure can be drawn as shown above.
Height of the wall = AD = AC = (AB + 3) or AB = (AC – 3).
In right-angled triangle ABC, AB2 + BC2 = AC2.
Thus, (AC – 3)2 + 81 = AC2.
∴ AC = 15 m.
Hence, height of the wall = 15 m.
Hence, option (b).
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