HOMEWORK QUESTION PLEASE!!!!!!!! HELP!!!!!!?

Question

it's about mean, mode, median.

12) Bill"s scores on his first four science tests are 84,86,90,91

what test scores must bill earn on the 5th test so that his average (mean) will be exactly 88?

13) Sue's average for 9 games of bowling is 108.

what is the lowest score she can recieve for the 10th game to have an average 110?????

PLEASE PLEASE PLEASE HELP ME!

Answer 1

It's just algebra.

To find the mean you add up all the scores and divide by 5, but since you're missing a number just use X.

(84+86+90+91+X)/5 = 88

Multiply both sides by five and add everything together:

351+X = 440

X = 89

Second problem

You don't know what the scores were so you start with the equation

X/9 = 108

Solve for X you get X = 972

That is the total of the first 9 scores

She played one more game with the average 110, you use the equation

(972+X)/10 = 110

X is the value of the score for the 10th game

Solve for X you get X = 128

Answer 2

12) (84 + 86 + 90 + 91 + x)/5 = 88

multiply both sides by 5 to cancel out the division on the left.

(84 + 86 + 90 + 91 + x) = 440

351 + x = 440

x = 89, subtract 351 from both sides.

13) 108 is the average of the first 9 games, so multiply 108 by 9 to get the total of the first 9 games: 9 * 108 = 972.  then the total of the first 9 games plus the tenth divided by 10 needs to equal 110.

(972 + x)/10 = 110

972 + x = 1100

x = 128

Answer 3

The answer to #12 is 89. I have no idea about the second one.

Answer 4

12) Bill must get an 89%

13) Sue must shoot a 112.

Answer 5

1)

To find the total score:

88*5=440

So, just subtract the scores frm the total

440-84-86-90-91=89

Answer=89

2) Use the same method

110*10=1100

1100-(9*108)

=1100-972

=128

Answer=128

Answer 6

12. (84+86+90+91+x)/5=88

      (84+86+90+91+x)=88*5=440

      351+x=440

      x=89

89

13. (108*9+x)/10=110

      (108*9+x)=1100

      972+x=1100

      x= 1100-972= 128

128