The average height of 3 people is 145cm. Two are the same height and one is 15 cm taller. What are the three heights?

Question

I believe the answer is 140, 140, and 155.  How do I show my work?

Answer 1

Shawn, how do we find average? We add the numbers and divide the total by the number of numbers, right?

 

Let's call the height of each of the two who are the same height h. If we set up the equation...

 

(h +h + h + 15)/3 = 145

 

First, we multiply by 3. I'll also combine the h's

 

3h + 15 = 435

         3h = 420

           h = 140.

 

So, you were correct! The tallest is h + 15 = 140 + 15 = 155.

 

 

Answer 2

145 = (x + x + x + 15)/3

 

Answer 3

For the sake of simplicity, I'm giving them names. :)

 

(John + Jan + Dan) / 3 = 145

 

Since John and Jan weigh the same, they can be represented by "a", and since Dan weighs 15 more than the other two, he can be represented by a + 15.

 

[a + a + (a + 15)] / 3 = 145

      [3a + 15] / 3 = 145

        a + 5    = 145

             -5       -5

            a      = 140

 

So the first two do weigh 140, and the other one weighs 155. Your answer is correct!