Ekskovatr can dig out a ditch 20 meters long in 1 hour. One ditch was dug by 10 hours, and other 12 hours. Find the total length of ditches which dug out, to a kotoryya dug out during this time. Solve a problem in different ways.

The first way to put all spent time and to increase by 20 m as in 1 hour of 20 m 1)10+12=22 (hour) - the spent time 2)22*20=440(m) - length of ditches the second way 1) 10*20=200(m) - length of 1 ditch. 2) 12*20=240(m) length is 2 ditches 3)200+240=440(m) of all
Answer add