A certain car uses 12 gallons of gasoline in traveling 120 miles. In order for the car to travel the same distance using 10 gallons of gasoline, by how many miles per gallon must the car's gas mileage be increased?
Options:
(A) 2
(B) 4
(C) 6
(D) 8
(E) 10

120/10 = 12. The difference is 12- 10 = 2. So the answer is: (A).

How much 60% of 50 is greater than 40% of 30?
Options:
(A) 18
(B) 55
(C) 33
(D) 22
(E) 11

(60/100) * 50 (40/100) * 30
30 - 12 = 18 So the answer is: (A).

A man walks at a speed of 3 km/hr and runs at a speed of 7 km/hr. How much time will the man require to cover a distance of 10 1/2 km, if he completes half of the distance, i.e., (5 1/4) km on foot and the other half by running?
Options:
(A) 2 1/2
(B) 2 1/6
(C) 4 1/2
(D) 2 1/1
(E) 2 1/8

Required time = (5 1/4)/3 + (5 1/4)/7 = 2 1/2 hours. So the answer is: (A).

Three years ago, the average age of a family of 5 members was 17. A baby having been born, the average age of the family is the same today. What is the age of the child?
Options:
(A) 3
(B) 2
(C) 4
(D) 1
(E) 5
Present age of 5 members = 5 x 17 + 3 x 5 = 100 years
Also, present ages of 5 members + Age of the baby = 6 x 17 = 102 years
Age of the baby = 102 100 = 2 years. So the answer is: (B).