The average temperature of the week is 80 degrees. The first 3 days have an average of 78 and the average of the last 3 days is 82 degrees, what was the temperature of the middle day?

80

Step-by-step explanation:Solution:

step 1 Address the formula, input parameters & values.

Input parameters & values:

The given numbers are 78 & 80

step 2 Find the sum of the given two numbers.

sum = 78 + 80 = 158

step 3 Divide the sum by 2 to get the average.

average = 158/2

= 79

Thus, 79 is an average of positive integers 78 and 80.

(b) 240

step-by-step explanation:

first, we use the pythagorean formula using the given side lengths to find x. then we use x to find the side lengths. then we add the side lengths to find the perimeter.

pythagorean theorem formula:

a^2 + b^2 = c^2

(x - 20)^2 + (x - 40)^2 = x^2

x^2 - 40x + 400 + x^2 - 80x + 1600 = x^2

x^2 -120x + 2000 = 0

(x - 100)(x - 20) = 0

x - 100 = 0 or x - 20 = 0

x = 100 or x = 20

we see that the solution x = 20 must be discarded because it will give a negative side length and a side length of 0. the only valid solution is x = 100.

perimeter = sum of the lengths of the sides

perimeter = x + x - 20 + x - 40

perimeter = 3x - 60

replace x with 100.

perimeter = 3(100) - 60

perimeter = 300 - 60

perimeter = 240