To solve this problem, we must remember that there are 12 months in a year. To find the number of months in 3 years, we must multiply the number of months in a year (12) by the number of years (3).
12 * 3 = 36
Now, if we lease the car at $605 per month, we must multiply this number by the number of months leased (36) in order to find the total cost of the lease. Since this is an estimate, we can round 36 to 35 and $605 to $600 in order to make our computations easier.
$605 * 36 ≈ $600 * 35 = $21,000
Therefore, a good estimate for the lease is $21,000. If we want to check our work, we can always compute how much the lease would actually cost by solving $605 * 36 = $21,780. Because these two numbers are relatively close, we can infer that our estimate is reasonable.
Hope this helps!