In a P6 Mathematics class at Greenwood Primary, the mean mark of the $8$ girls is $76$ and the mean mark of the $12$ boys is $70$. What is the mean mark of all $20$ students?
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Worked Solution
Step 1: Recall the formula: $\\text{mean} = \\dfrac{\\text{total of all values}}{\\text{number of values}}$.\n
Step 2: Find the total marks of the 8 girls: $8 \\times 76 = 608$.\n
Step 3: Find the total marks of the 12 boys: $12 \\times 70 = 840$.\n
Step 4: Combined total marks of all 20 students: $608 + 840 = 1448$.\n
Step 5: Combined mean = $1448 \\div 20 = 72.4$.\nCheck: $72.4 \\times 20 = 1448$, and $1448 - 840 = 608 = 8 \\times 76$. ✓
Answer: 72.4
Correct answer: 72.4
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