SAT Math Multiple Choice Practice Question 171: Answer and Explanation
17. At a family reunion, 4 men have a grandson present, 12 have a son present, and 21 have a father present. What is the minimum number of men that could be at the reunion?
Correct Answer: B
B. Four grandfathers are at the reunion. Because every one of them is also a father, include them in the 12 men who have a son present. That leaves 12 - 4 = 8 other men who have a son present. These 8 men could all be the grandfathers' children, so they can be counted in the 21 men who have fathers present. That leaves 21 - 8 = 13 men in the youngest generation. In total, you have 13 + 8 + 4 = 25 men.