Answer:
The student must score at least 76 in the third subject
Step-by-step explanation:
Given
Scores in 2 subjects = 77 and 72
Number of subjects = 3
Required
Determine the scores in the third subject to get an average of 75
Represent the score in the third subject with y
Average in 3 scores is calculated as thus;
[tex]Average = \frac{Sum\ of\ 3\ scores}{3}[/tex]
Substitute 75 for Average
[tex]75 = \frac{Sum\ of\ 3\ scores}{3}[/tex]
Multiply both sides by 3
[tex]3 * 75 = \frac{Sum\ of\ 3\ scores}{3} * 3[/tex]
[tex]3 * 75 = Sum\ of\ 3\ scores[/tex]
[tex]225 = Sum\ of\ 3\ scores[/tex]
Substitute (77 + 72 + y) for Sum of 3 scores
[tex]225 = 77 + 72 + y[/tex]
[tex]225 = 149 + y[/tex]
Subtract 149 from both sides
[tex]225 - 149 = 149 - 149 + y[/tex]
[tex]225 - 149 = y[/tex]
[tex]76= y[/tex]
[tex]y = 76[/tex]
Hence, the student must score at least 76 in the third subject
