SOLUTION: two- way radio range two children own two-way radios that have a maximum range of 2 miles.Once leaves a certain point at 1:00 pm. Walking due north at a rate of 4 mi/hr. The oth

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Question 4685: two- way radio range
two children own two-way radios that have a maximum range of 2 miles.Once leaves a certain point at 1:00 pm. Walking due north at a rate of 4 mi/hr. The other leaves the same point at 1:15 pm. Travling due south at 6 mi/hr. When will they be unable to communicate with each other?
Answer by xcentaur(357) About Me  (Show Source):
You can put this solution on YOUR website!
Time when the first child leaves (T1) =1:00 pm
Speed of first child (S1) = 4 mi/hr


Time when second child leaves (T2) = 1:15 pm
Speed of second child (S2) = 6 mi/hr


Time elapsed until second child leaves=T2-T1=15 minutes
Distance travelled by first child in that time=s1*15 minutes
=4 mi/hr * (1/4)hr
=1 mile


Range of radio=2 miles
Distance between children at 1.15 pm = 1 mile
Remaining range=1 mile


first child and second child are moving in opposite directions hence both distances must be considered


s=d/t => d=t*s


(distanceNorth)+(distanceSouth)=1 mile
t(S1)+t(S2)=1 mile
t(S1+S2)=1 mile
t(4+6)=1
t(10)=1
t=1/10 hour=60/10 minutes=6 minutes


Thus,10 minutes later the remaining range of 1 mile would also be passed.
Time at that moment = 1.15+6 minutes = 1:21 pm


Ans: After 1:21 pm,they will be unable to communicate with each other.