A watch lost 1 minute 18 seconds in 39 days. How many seconds did it lose per day?
To find out how many seconds the watch lost per day, we need to determine the total number of seconds it lost in 39 days first.
There are 60 seconds in a minute, so 1 minute 18 seconds is equal to 60 + 18 = <<1*60+18=78>>78 seconds.
In 39 days, the watch lost a total of 78 * 39 = <<78*39=3042>>3042 seconds.
To find out how many seconds it lost per day, we divide the total number of seconds lost by the number of days: 3042 / 39 = <<3042/39=78>>78 seconds.
Therefore, the watch lost 78 seconds per day.