If your string is 8 inches long, and each bead is 2 inches long, you can work out the amount of beads able to fit on the string by doing the following:
Because you have the string length (8 inches) and you know your beads are 2 inches big, you can work it out by doing
8 ÷ 2 = 4
Another way to check this simply doing:
2 + 2 = 4
4 is less than 8 so we know we can keep going
2 + 2 + 2 = 6
6 is still less than 8 so we can do one more
2 + 2 + 2 + 2 = 8
8 is the maximum amount because the length of the string is 8 inches long. Therefore we can see we put 2 in the equation four times, so the answer is 4.
Hope this helped! :)