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Four numbers are written in a row. the average of the first two is 21, the average of the middle two is 26, and the average of the last two is 30. what is the average of the first and last of the numbers?
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(a) 24. (b) 25. (c) 26. (d) 27. (e) 28.

Respuesta :

facundo3141592

Using the 3 given means, we can see that the mean of the first and last digits is 25, so the correct option is b.

What is the average of the last two numbers?

We have 4 numbers:

a, b, c, d.

We know that:

  • (a + b)/2 = 21
  • (b + c)/2 = 26
  • (c + d)/2 = 30

And we want to get

(a + d)/2

We can write this as:

(a + b)/2 - (b + c)/2 + (c + d)/2 = 21 - 26 + 30 = 25

The correct option is b.

If you want to learn more about means you can read:

https://brainly.com/question/14532771

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