SOLUTION: I can not figure out the expression for my son homework: "A fire currently covers 420 acres and continue to spread at a rate 60 acres per day. a. write the expression for the to

Algebra ->  Expressions-with-variables -> SOLUTION: I can not figure out the expression for my son homework: "A fire currently covers 420 acres and continue to spread at a rate 60 acres per day. a. write the expression for the to      Log On


   



Question 789137: I can not figure out the expression for my son homework:
"A fire currently covers 420 acres and continue to spread at a rate 60 acres per day.
a. write the expression for the total area covered by the fire in d days.
b. The firefighter estimate that they can put out the fire at a rate 80 acres per day. Write expression for the total area can put out fire in d days.
c. let the expression in a = expression in b. solve for d.
Please help. Thanks much.

Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
Part "a" could make sense if you try to think about the units, and also try to simulate what is happening (mentally) as you read the description.

At some time 0 days, fire covers 420 acres. In day 1, fire covers 420%2B1%2A60 acres; in day 2, fire covers 420%2B2%2A60 acres; and this pattern is easier to see than may be others are easy to see... In day d, the fire covers 420%2Bd%2A60 acres; but you would write this expression as 420%2B60d acres.