A.......B.......T : (B diem quay lai)
10' =1/6(h)=>AB=12/6=2(km)
v1/v2=12/6=2
=>(2AB+BT)/BT=2
=>BT=2AB=4(km)
t2=4/6=40'
a)
hai ban truong :6h30+10'+40'=7h20'
(Đến đúng giờ hay trễ học? thieu du kien)
b)
AT=AB+BT=2+4=6(km)
c)
(thieu du kien tg vao hoc?)