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ఒక విద్యార్థి యొక్క మార్కులు తప్పుగా 70కి బదులుగా 34గా నమోదు చేయబడ్డాయి. దీని కారణంగా, తరగతి సగటు మార్కులు 34 తగ్గాయి. తరగతిలో విద్యార్థుల సంఖ్య ఎంత?
28
32
27
23
28
Calculate the total discrepancy (70 - 34 = 36) and divide it by the change in average (4/3). Thus, 36 / (4/3) = 36 * 3 / 4 = 27.
Correct marks = 70, Incorrect marks = 34, Decrease in average = 4/3
n=Change in averageDifference in marks
Calculate the total discrepancy (70 - 34 = 36) and divide it by the change in average (4/3). Thus, 36 / (4/3) = 36 * 3 / 4 = 27.
Students often subtract 70 from 34 to get -36, forgetting that the magnitude of the total change is what dictates the shift in average.
Calculate the difference in marks
Find the absolute difference between the correct and incorrect marks to determine the total impact on the sum of scores.
36=70−34
Apply the average formula relationship
Since the total change in the sum of marks is equal to the number of students (n) multiplied by the change in average (ΔA), we rearrange the formula to find n.
n=4/336
Solve for the number of students
Multiply the numerator by the reciprocal of the fraction to isolate the number of students.
n=36×43=9×3=27
C is correct because the calculation of total difference (36) divided by the average decrement (4/3) results in 27 students.
This concept of 'Total Change = Difference per unit × Number of units' is identical to solving problems on displacement of average weights or ages, often seen in RRB exams.
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