Wei Ming's mean score over his first $5$ weekly spelling tests was $78$ marks. After his $6$th test, his mean score DROPPED to $76$ marks. What did Wei Ming score on his $6$th test?
Show Worked Solution
Worked Solution
Step 1: Recall the relationship $\text{total} = \text{average} \times \text{number of values}$. Build a total for the FIRST 5 tests and another for ALL 6 tests, then subtract.\n
Step 2: Total of first 5 tests = $5 \times 78 = 390$ marks.\n
Step 3: Total of all 6 tests = $6 \times 76 = 456$ marks.\n
Step 4: The 6th test score = (total of 6) − (total of 5) = $456 - 390 = 66$ marks.\nCheck: New mean = $(390 + 66) \div 6 = 456 \div 6 = 76$ ✓; old mean = $390 \div 5 = 78$ ✓.
Answer: 66 marks
Correct answer: 66 marks
Want more questions like this? Superholic Lab has 10,000+ MOE-aligned questions with full worked solutions.
Start Free Trial — 7 Days Free