If there is a total of 12 black beads out of a total of x number of beads, and the black beads make up 30%, then it means the 100% of beads is x.
Mathematically expressed,
12 = 30%
While,
x = 100%
This can now be expressed as follows;
12/x = 30/100
Since 12 is 30 perscent of the total which is x, then expressing 12 as a percentage of the total (which is unknown) is equal to expressing 30 as a percentage of 100.
12/x = 30/100
You cross multiply and you now have;
12 * 100 = x * 30
1200 = 30x
Divide both sides of the equation by 30 and you now have;
40 = x
Therefore you have a total of 40 beads (out of which 12 are black beads)
