Q15 of 99 Page 267

Maria cycling at a speed of 18 km per hour covers along the perimeter of an equilateral triangular field in 10 minutes. Let us write by calculating the time required for Maria to go directly to the midpoint of the side of the field starting from its opposite vertex. (√3 ≅ 1.732)

Given, the field is equilateral triangle


Let the side of triangle be x cm then each side of triangle = x km


She travels at speed of 18km/hour


⇒ She travels at the speed of 3 km in 10 minutes (


⇒


⇒ Distance she covers in 10 minutes = 3 × 10 = 30 km


Now according to the given condition


3x = 30


⇒ x = 10


Now each side of equilateral triangle = 10km


Midpoint of the side of the field directly from the opposite vertex means the perpendicular distance to that side which is also the height of the triangle


Area of triangle = 1/2 × base × height


⇒


⇒


⇒ h = km


=


= 0.3464 km


Time taken to cover this distance


Time


= 0.0192 hours


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