Question 1063933
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{{{(2*40)/(55-40)}}} = {{{80/15}}} = {{{5}}} {{{1/3}}} hours = 5 hours and 20 minutes.


2*40 in the numerator is the distance for Ted been ahead at the moment the father started his move/travel.


55 - 40 = 15 in the denominator is their relative speed (which is the rate of decreasing the distance between them).


The remaining explanation is the formula Time = {{{Distance/Rate}}}.


Solved.