Step 1: Arrange the numbers from least to greatest.
GIVEN: 13, 6, 10, r
r = ?
Mode = 13
Least to greatest.
6, 10, 13, (r =?)
Step 2: Find the missing number
NOTE: The mode is the number that appears most often.
From the definition
6 - 1 time
10 - 1 time
13 - 1 time
This all numbers are repeating only one time. so we can find the mode based
on the r value.
If r = 13
6, 10, 13, 13
The number that appears most often is 13. When r = 13, the mode is 13.
( If you take r = 6 or 10, then 6 or 10 will become mode. but in the question
they given the mode as 13, So I took r = 13)