Math Problem Statement

In a class, a Science test was conducted by Prof. More. The number of students scoring 55 or less than 55 marks is 24. The number of students scoring more than 55 marks is at the most 32. What is the smallest possible average score of the students scoring more than 55 marks if the average score of all the students in the class is 71 marks?

Solution

Let the total number of students in the class be denoted by NN. We are given that:

  • The number of students scoring 5555 marks or less is 24.
  • The number of students scoring more than 55 marks is at most 32.
  • The average score of all the students is 71 marks.

Let:

  • N1=24N_1 = 24 be the number of students scoring 55 or less.
  • N232N_2 \leq 32 be the number of students scoring more than 55 marks. So, the total number of students N=N1+N2N = N_1 + N_2.

Step 1: Setting up the total score equation

Let the total score of students scoring 55 or less be S1S_1, and their average score be 55 or less. Since there are 24 students, we can denote the total score as:

S124×55=1320S_1 \leq 24 \times 55 = 1320

Let the total score of students scoring more than 55 be S2S_2. The average score of all the students is 71 marks, so the total score of all students is:

S1+S2=71×NS_1 + S_2 = 71 \times N

Thus, we have the equation:

S1+S2=71×(N1+N2)S_1 + S_2 = 71 \times (N_1 + N_2) S1+S2=71×(24+N2)S_1 + S_2 = 71 \times (24 + N_2)

Step 2: Maximizing the total score of students scoring 55 or less

To minimize the average score of students scoring more than 55 marks, we should assume that the students scoring 55 or less have the highest possible score (because the higher the score of the 55-or-less group, the lower the score required by the more-than-55 group to maintain the overall average).

Thus, the total score of students scoring 55 or less is S1=1320S_1 = 1320.

Step 3: Calculating the score of students scoring more than 55

Substitute S1=1320S_1 = 1320 into the equation S1+S2=71×(24+N2)S_1 + S_2 = 71 \times (24 + N_2):

1320+S2=71×(24+N2)1320 + S_2 = 71 \times (24 + N_2) S2=71×(24+N2)1320S_2 = 71 \times (24 + N_2) - 1320 [ S_2 = 1704 + 71N

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Math Problem Analysis

Mathematical Concepts

Algebra
Average Calculation
Inequalities

Formulas

Total score = (average score) × (number of students)
S_1 + S_2 = 71 × (N_1 + N_2)
S_1 ≤ 24 × 55

Theorems

Basic Inequality Theorem

Suitable Grade Level

Grades 10-12