Spark plugs should be charged every 15,000 miles. if a truck runs 5,000 miles a month, how many times a year should the spark plugs be changed

One month = 5000

Number of months before the spark plugs need to change :

15000 ÷ 5000 = 3

The sparks can last 3 months before it needs to be changed.

Number of times it need to change in a year = 12 ÷ 3 = 4


Answer : It needs to be change 4 times a year.