The average mark of Hakim and Nadia is 64. When Priya's mark is included, the average of all three increases to 70. When Ravi's mark is also included, the average of all four drops to 67. What is Ravi's mark?
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Worked Solution
Step 1: Find the total mark of Hakim and Nadia.
Average of 2 = 64, so total = 64 × 2 = 128
Step 2: Find Priya's mark using the 3-person average.
Average of 3 = 70, so total of 3 = 70 × 3 = 210
Priya's mark = 210 − 128 = 82
Step 3: Find the total mark of all four.
Average of 4 = 67, so total of 4 = 67 × 4 = 268
Step 4: Find Ravi's mark.
Ravi's mark = 268 − 210 = 58
Step 5: Verify.
128 + 82 + 58 = 268. 268 ÷ 4 = 67. ✓
Answer: 58
Correct answer: 58
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