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October 2nd, 2019, 11:23 PM   #1
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How to find average speed for this problem?

What is the average speed of a man who travels 1/4th distance at 10kmph, 1/3rd the distance at 20kmph and the rest at 12.5 kmph?

Solution: Remaining time = 1 – (1/4 + 1/3) = 5/12

Multiplying 12 to fractions to get whole numbers; 3, 4 & 5.

After this how to proceed?
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October 3rd, 2019, 02:52 AM   #2
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Math Focus: Area of Circle
Let the total distance be x.
Travels

(i) $1/4 \; distance \; at \; 10km/h \; t_0= \dfrac{x}{4} : 10 = \dfrac{x}{40}$

(ii) $1/3 \; distance \; at \; 20km/h \; t_1 = \dfrac{x}{60}$

(iii) $5/12 \; distance \; at \; 12.5km/h \; t_2 = \dfrac{x}{30}$

The total time it took $t_{total} = \dfrac{x}{40} + \dfrac{x}{60} + \dfrac{x}{30} = \dfrac{9x}{120} = \dfrac{3x}{40}$

Average velocity is the total distance divided by total time: $x: \dfrac{3x}{40}=\dfrac{40}{3}=13 \dfrac{1}{3}$
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