Question

A student wrote three papers in mathematics examination marks for two papers we're 77and 72 respectively.to obtain grade A, an average of not less than 75marks is required for the three papers

Answer 1

The student must score at least 76 in the third subject

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;

`Average = (Sum\ of\ 3\ scores)/(3)`

Substitute 75 for Average

`75 = (Sum\ of\ 3\ scores)/(3)`

Multiply both sides by 3

`3 * 75 = (Sum\ of\ 3\ scores)/(3) * 3`

`3 * 75 = Sum\ of\ 3\ scores`

`225 = Sum\ of\ 3\ scores`

Substitute (77 + 72 + y) for Sum of 3 scores

`225 = 77 + 72 + y`

`225 = 149 + y`

Subtract 149 from both sides

`225 - 149 = 149 - 149 + y`

`225 - 149 = y`

`76= y`

`y = 76`

Hence, the student must score at least 76 in the third subject