Category: Quantitative Reasoning
Difficulty: Easy
Result: Wrong
4. Mary, who is sixteen years old, is four times as old as her brother. How old will Mary be when she is twice as old as her brother?
- 20
- 24◀ Correct Answer
- 25
- 26
- 28
This question tests your quantitative reasoning skills by requiring you to set up and solve algebraic equations based on given relationships. Currently, Mary is 16 years old, and she is four times as old as her brother. Therefore, her brother is 16 / 4 = 4 years old. The age difference between Mary and her brother is 16 - 4 = 12 years. We need to find out when Mary will be twice as old as her brother. Let x be the number of years in the future when this occurs. Then, Mary's age will be 16 + x, and her brother's age will be 4 + x. Setting up the equation: 16 + x = 2 * (4 + x). Simplifying, we get 16 + x = 8 + 2x. Subtracting x from both sides: 16 = 8 + x. Subtracting 8 from both sides: 8 = x. So, in 8 years, Mary will be 16 + 8 = 24 years old, and her brother will be 4 + 8 = 12 years old. At that time, Mary will be twice as old as her brother. Therefore, the correct answer is 24.