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dans parents are going to pay for half his car if he gets a 90 average in math for all four marking periods and the final exam. Here are his grades for the first four quarters: 91,83,90 and 89. What grade does he need on his final exam to have a 90 average?

dans parents are going to pay for half his car if he gets a 90 average in math for all four marking periods and the final exam Here are his grades for the first class=

Respuesta :

charlief22

Answer:

Above 97.

Step-by-step explanation:

The average of something is the total values divided by the number of values added together so:

Step 1 - Add the four values together:

Let x be the unknown final exam grade

91 + 83 + 90 + 89 + x

353 + x

Step 2 - Find the average value:

[tex]\frac{353 + x}{5} = 90[/tex]

Step 3 - Simplify by multiplying both sides by 5:

[tex]\frac{353 + x}{5} * 5 = 90 * 5[/tex]

[tex]353 + x = 450[/tex]

Step 4 - Isolate x:

[tex]353 + x = 450[/tex]

x = 450 - 353

x = 97

So his grade must be above 97.

Hope this helps!

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