Question

Ali sorced 66 and 72 marks respectively.For his two tests what is the lowest mark he must have sorced for his third test.If an average sorce of a least 75 is requied to qualify for a bouns prize

Answer 1

Answer:

87

Step-by-step explanation:

66 + 72 + 87 = 225

225/3 = 87

Answer 2

Answer:

  87

Step-by-step explanation:

For problems involving averages, it often works well to consider the differences from the average. Here, Ali desires an average of 75. The total of differences from average will be zero. The differences for the known scores are ...

  66 -75 = -9

  72 -75 = -3

The total of these is -12, so the third score must have a difference of +12 for the average to be 75

  x -75 = 12

  x = 87

For the average to be at least 75, the third score must be at least 87.

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You can also work this in a more conventional way. The average of the three scores must be at least 75.

  (66 +72 +x)/3 ≥ 75

  138 +x ≥ 225 . . . . . . multiply by 3, simplify

  x ≥ 87 . . . . . . . . . . subtract 138

The lowest mark Ali must receive is 87.