If you worry about changing of batteries then you don’t worry too much because with the power of water the calculators are functioning. All what you have to operate this calculator is water, pour some water in the panel of this calculator and then close with stopper given by them.

The water inside the calculator generates enough power for calculating various functions. The water never cause harm to human but by using water in the calculator a small leak will spoil the entire calculator. Definitely this product is gives us more eco-friendly. The price of the calculator is approximately $9.
Via: Keetsa