Install street lamps (installed at both ends) on both sides of the street with a total length of 2 kilometers, and install one every 50 meters. A * * *, how many lights should be installed?
2 kilometers =2000 meters,
2000÷50=40 (pieces),
(40+ 1)×2=82 (lamp),
A: A * * * needs to prepare 82 street lamps.