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Time when the first child leaves (T1) =1:00 pm
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document.write( "Time when second child leaves (T2) = 1:15 pm
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document.write( "Speed of second child (S2) = 6 mi/hr
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document.write( "Time elapsed until second child leaves=T2-T1=15 minutes
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document.write( "Distance travelled by first child in that time=s1*15 minutes
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document.write( "=4 mi/hr * (1/4)hr
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document.write( "=1 mile\r
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document.write( "Range of radio=2 miles
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document.write( "Distance between children at 1.15 pm = 1 mile
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document.write( "Remaining range=1 mile
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document.write( "first child and second child are moving in opposite directions hence both distances must be considered\r
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document.write( "s=d/t => d=t*s\r
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document.write( "(distanceNorth)+(distanceSouth)=1 mile
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document.write( "t(S1)+t(S2)=1 mile
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document.write( "t(S1+S2)=1 mile
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document.write( "t(4+6)=1
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document.write( "t(10)=1
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document.write( "t=1/10 hour=60/10 minutes=6 minutes\r
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document.write( "Thus,10 minutes later the remaining range of 1 mile would also be passed.
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document.write( "Time at that moment = 1.15+6 minutes = 1:21 pm\r
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document.write( "Ans: After 1:21 pm,they will be unable to communicate with each other.\r
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