Smith travels along four sides of a square at speeds of 10, 12, 15 and

1.	Smith travels along four sides of a square at speeds of 10, 12, 15 and 20 km/hr. The average speed of the Smith is:1. \(13\frac{1}{3}\) km/hr2. \(12\frac{1}{2}\) km/hr3. \(14\frac{1}{4}\) km/hr4. 10 km/hr
Answer» Correct Answer - Option 1 : \(13\frac{1}{3}\) km/hr Given Smith travels at speeds of 10 km/hr, 12 km/hr, 15 km/hr, 20 km/hr along sides of the square Formula used Average speed =\(\frac{{total\;distance\;}}{{total\;time}}\) Calculation Let assume that side of square be x ⇒ Total distance = perimeter of square ⇒ 4x ⇒ Total time = \(\frac{x}{{10}}+\frac{x}{{12}}+\;\frac{x}{{15}}+\frac{x}{{20}}\) ⇒ \(\frac{{18x}}{{60}}\) ⇒ Average speed = total distance / total time ⇒ \(\frac{{4x}}{{\frac{{18x}}{{60}}}}\) ⇒ \(\frac{{40}}{3}\;km/hr\) ⇒ \(13\frac{{\;\;1\;\;}}{3}\;km/hr\)

Smith travels along four sides of a square at speeds of 10, 12, 15 and 20 km/hr. The average speed of the Smith is:1. \(13\frac{1}{3}\) km/hr2. \(12\frac{1}{2}\) km/hr3. \(14\frac{1}{4}\) km/hr4. 10 km/hr

Answer» Correct Answer - Option 1 : \(13\frac{1}{3}\) km/hr

Given

Smith travels at speeds of 10 km/hr, 12 km/hr, 15 km/hr, 20 km/hr along sides of the square

Formula used

Average speed =\(\frac{{total\;distance\;}}{{total\;time}}\)

Calculation

Let assume that side of square be x

⇒ Total distance = perimeter of square

⇒ 4x

⇒ Total time = \(\frac{x}{{10}}+\frac{x}{{12}}+\;\frac{x}{{15}}+\frac{x}{{20}}\)

⇒ \(\frac{{18x}}{{60}}\)

⇒ Average speed = total distance / total time

⇒ \(\frac{{4x}}{{\frac{{18x}}{{60}}}}\)

⇒ \(\frac{{40}}{3}\;km/hr\)

⇒ \(13\frac{{\;\;1\;\;}}{3}\;km/hr\)

Discussion

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