5
Q's age is equidistant from R's age and T's age (Q is younger than R by the same amount Q is older than T). If the total of R's and T's ages is 50 years, what is the exact difference between R's and Q's age?
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Solution: Step 1: Express the first condition: Q is as much younger than R as he is older than T. This translates to R - Q = Q - T.
Step 2: Rearrange the equation from Step 1: R + T = 2Q.
Step 3: Use the second condition: The sum of the ages of R and T is 50 years. So, R + T = 50.
Step 4: Substitute R + T = 50 into the equation from Step 2: 50 = 2Q.
Step 5: Solve for Q: Q = 50 / 2 = 25 years.
Step 6: The question asks for the difference between R and Q's age, which is (R - Q).
Step 7: While we know Q's age (25), we do not have sufficient information to determine R's age (or T's age individually, only their sum). For example, if R=30, T=20, then R-Q = 5. If R=40, T=10, then R-Q = 15. The difference varies.
Step 8: Therefore, the difference between R and Q's age cannot be definitely determined from the given information.
11
Mr. Joe's family includes himself, his wife, and their four children. The average family age immediately after the birth of the first, second, third, and fourth child was 16, 15, 16, and 15 years, respectively. Given that the current average age of the entire six-person family is 16 years, what is the age of Mr. Joe's eldest son?
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Solution: Step 1: At 1st child's birth (3 members): Total age = 16 * 3 = 48 years.
Step 2: At 2nd child's birth (4 members): Total age = 15 * 4 = 60 years.
Step 3: Time elapsed between 1st and 2nd child's birth = (60 - 48) / 3 = 12 / 3 = 4 years. Eldest son's age at 2nd child's birth = 4 years.
Step 4: At 3rd child's birth (5 members): Total age = 16 * 5 = 80 years.
Step 5: Time elapsed between 2nd and 3rd child's birth = (80 - 60) / 4 = 20 / 4 = 5 years. Eldest son's age at 3rd child's birth = 4 + 5 = 9 years.
Step 6: At 4th child's birth (6 members): Total age = 15 * 6 = 90 years.
Step 7: Time elapsed between 3rd and 4th child's birth = (90 - 80) / 5 = 10 / 5 = 2 years. Eldest son's age at 4th child's birth = 9 + 2 = 11 years.
Step 8: At Present (6 members): Total age = 16 * 6 = 96 years.
Step 9: Time elapsed between 4th child's birth and present = (96 - 90) / 6 = 6 / 6 = 1 year.
Step 10: Present age of eldest son = 11 + 1 = 12 years.
13
The average age of four boys, A, B, C, and D, is 5 years. The average age of A, B, D, and E is 6 years. Given that C is 8 years old, what is the age of E?
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Solution: Step 1: From the first statement, the total age of A, B, C, and D is: 4 members × 5 years/member = 20 years (A + B + C + D = 20).
Step 2: From the second statement, the total age of A, B, D, and E is: 4 members × 6 years/member = 24 years (A + B + D + E = 24).
Step 3: Substitute C's age (8 years) into the first equation: A + B + 8 + D = 20.
Step 4: Simplify to find the sum of A, B, and D: A + B + D = 20 - 8 = 12 years.
Step 5: Substitute the sum (A + B + D = 12) into the second equation: 12 + E = 24.
Step 6: Solve for E: E = 24 - 12 = 12 years.
15
Five years ago, the average age of A, B, C, and D was 45 years. Now, with E joining them, the average age of all five individuals is 49 years. What is E's current age?
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Solution: Step 1: Calculate the total age of A, B, C, and D five years ago: Total_age_past = 4 people * 45 years/person = 180 years.
Step 2: Calculate their current total age. Each of the 4 people has aged 5 years, so their combined age increased by 4 * 5 = 20 years.
Total_current_age_ABCD = 180 years + 20 years = 200 years.
Step 3: After E joins, there are 5 people, and their average age is 49 years.
Step 4: Calculate the total current age of all five individuals (A, B, C, D, and E): Total_current_age_ABCDE = 5 people * 49 years/person = 245 years.
Step 5: The age of E is the difference between the total current age of five people and the total current age of A, B, C, and D.
Age of E = Total_current_age_ABCDE - Total_current_age_ABCD = 245 years - 200 years = 45 years.
20
What will be the ratio of Sam's age to Albert's age in 5 years?
I. Sam's current age exceeds Albert's current age by 4 years.
II. Albert's current age is 20 years.
III. The ratio of Albert's current age to Sam's current age is 5:6.
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Solution: Step 1: Let Sam's present age be S and Albert's present age be A. We need to find the ratio (S+5) : (A+5).
Step 2: Formulate equations:
From I: S = A + 4 (Eq 1)
From II: A = 20 (Eq 2)
From III: A / S = 5 / 6 => 6A = 5S (Eq 3)
Step 3: Check combinations for sufficiency:
* **I and II:** From (2), A=20. Substitute into (1): S = 20 + 4 = 24. So, S=24, A=20. Ages after 5 years: S+5=29, A+5=25. Ratio = 29:25. Sufficient.
* **II and III:** From (2), A=20. Substitute into (3): 6(20) = 5S => 120 = 5S => S = 24. So, S=24, A=20. Ages after 5 years: S+5=29, A+5=25. Ratio = 29:25. Sufficient.
* **I and III:** From (1), S = A + 4. Substitute into (3): 6A = 5(A + 4) => 6A = 5A + 20 => A = 20. Then S = 20 + 4 = 24. So, S=24, A=20. Ages after 5 years: S+5=29, A+5=25. Ratio = 29:25. Sufficient.
Step 4: Conclusion: Any two of the three statements are sufficient to determine the ratio between Sam and Albert's ages after 5 years.