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Solution to Problem 6
A shorter method for question 24 is to calculate the speeds in km/min. This gives overall speed approx. 1.25 km/min. So if distance between stations is less than 1.25 times the travel time in min, we will consider that for our answer. We can further reduce time taken for calculating individual speeds by converting the 1.25 factor to [1 + 0.25], in other words, [time + one-fourth of time], since it is easy to mentally calculate one-fourth of a number. Eg. for E to F, time = 75 min and distance = 106km. So we have 75*1.25 = 75 + (1/4)75 = 75 + (~)18 =~93. Because 106 > 93, we will not consider this for our answer. This calculation will be even easier for other values of the travel times (100, 80, 120).