Answer: Charlie have to drive at a speed of 80miles per hour in order to reach there on time.
Step-by-step explanation:
At 4pm Charlie realizes he has half an hour to get to his grandmothers house for diner. Knowing that the time he has left is 30 minutes and the distance to his grandmother's place is 40 miles, the only thing that he can control is his speed
Speed = distance travelled / time taken
40/0.5 = 80 miles per hour
So you need to compute all the rates to see which is the best deal.
$1.79/12.5ft^2=$0.1432 per ft^2
$5.29/40ft^2=$0.13225 per ft^2
$8.49/50ft^2=$0.1698 per ft^2
$6/60ft^2=$0.10 per ft^2
So the last option is the cheapes per square foot and thus is the best deal. Ordered from least to greatest.
Sherbert, blue, red, and green
34-13.6=20.4
20.4/34= .60
60% off