Convert 259 from decimal to binary. How many units does this number contain?

Let’s represent 259 as the sum of powers of two:
259 = 256 + 2 + 1 = 2 ^ 8 + 2 ^ 1 + 2 ^ 0
Imagine a plate with numbers from zero to eight, put these numbers in descending order and put ones on those positions, the degree of which is in the number 259, that is, on 8, 1 and 0. We get:
100000011
This number contains 3 units
Answer: 3.