Two poles of height 12 m and 20 m are fixed to a level ground. The distance between the bottom of the poles is 15 m. What is the distance (in m) between their tops?
- AOption (a)
20
- BOption (b)
17
- COption (c)
25
- DOption (d)
16
View answer & explanationHide answer & explanation
Correct answer
17
Why this answer is correct
Shortcut Trick
Vertical difference in height = 20 m − 12 m = 8 m
Horizontal distance between poles = 15 m
Distance between tops = √(82 + 152)
Using the standard Pythagorean triplet (8, 15, 17), the required distance is 17 m.
∴ The correct answer is 17 m.
Alternate Method
Given:
Height of first pole (AB) = 12 m
Height of second pole (CD) = 20 m
Distance between bases (BD) = 15 m
Formula Used:
Pythagoras Theorem: Hypotenuse2 = Base2 + Perpendicular2
Calculations:
⇒ Let the distance between the tops be 'x'.
⇒ Construct a horizontal line from the top of the shorter pole to the taller pole.
⇒ Base of the resulting triangle = 15 m
⇒ Height of the resulting triangle = 20 m − 12 m = 8 m
⇒ x2 = 152 + 82
⇒ x2 = 225 + 64
⇒ x2 = 289
⇒ x = √289
⇒ x = 17 m
∴ The correct answer is 17 m.
Additional Information
Pythagorean Triplets
These are sets of three positive integers (a, b, c) such that a2 + b2 = c2. Common triplets include (3, 4, 5), (5, 12, 13), (8, 15, 17), and (7, 24, 25).
Right-Angled Triangle Property
In a right-angled triangle, the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.
Level Ground Assumption
In height and distance problems, unless stated otherwise, vertical objects like poles, towers, and buildings are assumed to be perpendicular to the horizontal level ground (making a 90° angle).