Devi's average score over four mathematics papers at Bishan Primary School is 78 marks. To raise her average to exactly 80 marks after a fifth paper, what must she score on the fifth paper?
Show Worked Solution
Worked Solution
Step 1: Find the total marks across the first four papers.
Total of 4 papers = average × number = 78 × 4 = 312.
Step 2: Find the total marks needed across all five papers for an average of 80.
Total of 5 papers = 80 × 5 = 400.
Step 3: The fifth paper's score = new total − old total.
400 − 312 = 88.
Final answer: Devi must score 88 marks on the fifth paper.
Answer: 88
Correct answer: 88
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