The lever is in balance. It is acted upon by two forces F1 = 40 H, F2 = 50H. The fulcrum is 16cm from the left

The lever is in balance. It is acted upon by two forces F1 = 40 H, F2 = 50H. The fulcrum is 16cm from the left end of the arm. How long is the arm? Ignore the weight of the arm.

To comply with the equilibrium condition of the lever, the moments of forces of each shoulder must be equal to each other. The equality F1 * L1 = F2 * L2 must be fulfilled (L1 and L2 are the lever arms, or in other words, the distance from the fulcrum to the points of the applied force).
In the problem, it is not specified which arm length is known. Let’s consider two options.
1. Let L1 = 16cm, then
40 * 16 = 50 * L2
L2 = (40 * 16) / 50 = 12.8cm. The length of the entire arm is L = L1 + L2 = 16 + 12.8 = 28.8cm.
2. L2 = 16cm
40 * L1 = 50 * 16
L1 = (50 * 16) / 40 = 20cm. Lever length L = L1 + L2 = 20 + 16 = 36cm.