Answer:
3
Step-by-step explanation:
1600 miles × (1 gallon / 24 miles) = 66⅔ gallons
66⅔ gallons × (1 tank / 20 gallons) = 3⅓ tanks
Rounding up to the nearest integer, the family will need 4 tanks. Since they start with a full tank, they will need to stop at least 3 times.