Question

A set of 9 numbers {3, 3, 4, 5, 5, 5, 6, 7, 7} has a mean of 5. Another number is added to the set, and the mean becomes 6. What number is added to the set?

Answer 1

15

Explanation:

3 + 3+ 4+ 5+ 5+ 5+ 6+ 7+ 7=45

You would then divide that my 9(the amount of numbers) to get three

(3 + 3+ 4+ 5+ 5+ 5+ 6+ 7+ 7)/9

=3

If you are adding a number the numbers would be

3 + 3+ 4+ 5+ 5+ 5+ 6+ 7+ 7+?/10

Its ten because now you would have 10 numbers.

You know it equals 6, so you ask yourself: What divided by 10 would give you 6 or this equation:

( 3 + 3+ 4+ 5+ 5+ 5+ 6+ 7+ 7+?)/10=6

(45+?)/10=6

multiply both sides of the equal sign by 10

10(45+?)/10=6*10

The 10 on the bottom of the left side cancels out.

(45+?)=60

Subtract 15 from both sides of the equal sign

45+?-45=60-45

?=15