GMAT Problem Solving (PS) | Re: On a long drive, a truck covered P percent of the total

Q: Ask you to find the total average rate in terms of a percentage ex: P%

Step1: define P% and build your RTD chart

RTD
30(t1) = some portion of d (?)
50(t2) = some portion of d
(?) (tt) = total distance (d)

p% = the percentage of the total distance travelled at 30mph.
So I need (?)s from above. The total avg rate and the % distance at 30mph.

Step2: assign an easy split (50/50) for total distance (d). P = 50%

Step3: Break/solve the two pieces for t1 and t2 and add to get the total time (tt)
rtd=>
...

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