Answer:
it would take Charlie 4 1/2 months rounded up =5 month's to get $280.00
Step-by-step explanation:
already has 100 then if you do 4x4 =16 but since it is 40x40 it would be 160 plus the 100 they already had. but they would only need at least 280 so 260+20=280 but it says they save 40 (a month) so the answer would be 5 months