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Your math tests scores are 68 78 90 and 91. What is the lowest grade you can get on the next test to still have an average at least 85

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Respuesta :

Let x be your fifth grade. The average will be

[tex]\dfrac{68+78+90+91+x}{5}=\dfrac{327+x}{5}[/tex]

We want this average to be at least 85, so we have

[tex]\dfrac{327+x}{5}\geq 85[/tex]

Multiply both sides by 5:

[tex]327+x \geq 425[/tex]

Subtract 327 from both sides:

[tex]x \geq 98[/tex]

So, you need at least 98.

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