Question

Find missing number.
1 5, 10, 20, 10, ?, 15​

Answer 1

Answer:

answer is five in question mark

Answer 2

Here you see,

The first number is 10 and the third number is 15. So, the difference between them is 5(15–10=5).

The third number is 15 and the fifth number is 20. So, the difference between them is 5(20–15=5).

The fifth number is 20 and the seventh number is 25. So, the difference between them is 5(25–20=5).

So here, we can see a trend. The numbers in the odd places are increasing by 5.

Now, if wee look closely,

The second number is 5 and the fourth number is 0. so, the difference between them is 5(5–0=5).

So, we can see clearly that the numbers in the even places are decreasing by 5.

So, the sixth number will be (fourth number-5) = 0–5=-5

The missing number will be -5.
In short

10-5=5

5+10=15

15-15=0

0+20=20

20-25=-5

-5+30=25

So the missing number is -5