These questions are with only a 4-number series and look more complicated since there is no visible average pivot.

**Let’s see it again on an axis:**

**420_** 430**_440_**450 _460 _470 _480 _490 _**500** _510 _**520**

Notice that the first number, 420, is at the same distance from 440, as the last number, 520, is at the same distance from 500.

**420_ 430_440**_450 _460 _470 _480 _490 _**500** **_510 _****520**

Looking at the first and last numbers, or the highest and lowest in a number series is a quick way to determine whether a series of numbers is symmetrical.

In the case of a 4-number series, it’s definitely a symmetrical series.

If it’s a 5-number series, it’s probably symmetrical, you just need to confirm it with the 3 inner numbers.

So, back to the example, there are 4 numbers in a symmetrical series, so 420 and 520 neutralize each other, which makes calculating the average very easy since you need to take into consideration only the two inner numbers – 440 and 500.

~~420_ 430_~~440_450 _460 _470 _480 _490 _**500**~~ ~~**_510 _****520**

From here on it’s very easy to determine that 470 is the average

**440**_450 _460 _**470 **_480 _490 _**500**

If we will stick to the “looking at the distance” approach, 470 is the number right in the middle with the same distance from 440 and 500.

If the number series in the question is not symmetrical, you will need to calculate it in your head or use the scrap paper like in this example: