The mean of twelve positive numbers is 3. When another number is added, the mean becomes 5. Find the thirteenth number.

29

Step-by-step explanation:

Let a12 be the mean of the first 12 numbers:

a12=(sumOf12Numbers)/12.

So, sumOf12Numbers=12×a12

We add a new number, x:

a13=(sumOf12Numbers+x)/13

13×a13=12×a12+x

x=13×a13-12×a12=13×5-12×3=65-36=29

The thirteenth number is 29

The thirteenth number is 29

Step-by-step explanation: We shall by looking at the available bits of information. We already have a mean of 12 positive numbers which is 3. The addition of the numbers divided by 12 would result in the mean. This we can express as follows;

Summation/12 = 3

That basically is the formula for calculating a set of data/numbers.

If we cross multiply, the expression becomes;

Summation = 3 x 12

Summation = 36.

That means if we add up all 12 positive numbers we would have 36. When another is added the mean becomes 5. That is,

(36 + a)/13 = 5

That means the summation is now 36 + a, and the observed data is now 13, while the mean is now 5. Therefore,

(36 + a)/13 = 5

We cross multiply and we have,

36 + a = 5 x 13

36 + a = 65

Subtract 36 from both sides of the equation

a = 29

Therefore the 13th number is 29.

i think it's ф or x=6,-6

step-by-step explanation:

-x^2=-36

x^2=-36

ф

or

if you mean by : -(x^2)=-36

it'll be: x^2=36

x=6,x=-6

hope it'll ! have a good day!

you for asking!

b. 6

step-by-step explanation:

we are given the table representing an exponential function.

we can see from the table that, as x is increasing, the value of y is increasing in the power of 6.

i.e. the following relation is obtained,

x = 1, y = 6

x = 2, y = 36 =

x = 3, y = 216 =

x = 4, y = 1296 =

x = 5, y = 7776 =

so, the geometric series obtained is .

thus, the common ratio is given by = = 6.

hence, the common ratio is 6.