Question

Do you know how to do the first problem about biology test

Answer 1

86

Step-by-step explanation:

The mean is calculated as the sum of all the values divided by the number of values. If after 6 tests, the mean score is 72, we get:

`\begin{gathered} (x_1+x_2+x_3+x_4+x_5+x_6)/(6)=72 \\ x_1+x_2+x_3+x_4+x_5+x_6=72(6) \\ x_1+x_2+x_3+x_4+x_5+x_6=432 \end{gathered}`

Where x1, x2, x3, x4, x5, and x6 are the scores of the first six tests. So, we know that the sum of the scores of the first six tests is 432.

Now, we want that the mean of 7 tests raise to 74, so

`\frac{x_1+x_2+x_3+x_4+x_5+x_6+x_7_{}}{7}=74`

But we know that the sum of the first six tests is 432, so

`(432+x_7)/(7)=74`

Therefore, we can solve for x7

`\begin{gathered} 432+x_7=74(7) \\ 432+x_7=518 \\ x_7=518-432 \\ x_7=86 \end{gathered}`

So, Ruben need 86 on his next test.