doubt for word problem experts

Question

A man performs 3/5 of the total journey by rail 17/20 by bus and remaining 6.5 km on foot his total journey is ?

 

i know the answer and how to solve but i have doubt

please understand my doubt

a man performs 3/5 of the total journey by rail 17/20 by bus
now when we are assuming x as total journey
so we did as question directs to do
now 3/5 of total journey in math we do 3/5x, 3/5x he traveled by rail
now 17/20 by bus so conclusion is 17/20 he traveled by bus. they not state that 17/20 of total journey by bus then our in conclusion will be 17x/20

how i get to know that when should i take variable for multiply with fraction and when shouldn't or might have when i seen any fraction in word problem so it is understood that i have to multiplied with variable.

 

please send concrete solution 

Answer 1

as stated the problem doesn't seem to make sense

as 3/5 +17/20 > 1 which means 3/5 and 7/20 can't be fractional parts of the TOTAL distance.

so maybe it means 3/5 of the total then 17/20 of the remainder

that's 3/5 + 17/20)(2/5) = .6 +.14 = .74, leaving .26 to go and = to 6.5 km

6.5 km = .26 of the Total distance

T = 6.5/.26 = 25 km