A student's marks were wrongly entered as 83 instead of 63. Due to the error the average marks for the class got increased by 0.5. Find the number of students in the class.
উত্তর: গ) 40
- ক) 10
- খ) 20
- গ) 40
- ঘ) 73
ব্যাখ্যা
C) 40. The wrong entry put 83 − 63 = 20 extra marks into the class total. Shared across n students, those 20 marks lift the average by 20/n. Setting 20/n = 0.5 gives n = 40. Check: 20 ÷ 40 = 0.5, which matches the rise in the average.
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