Giving brainiest+points need explanation on this one my answer is 25 is it right?

Known facts:
A line shaft rotating at 250 rpm, a grinder shaft that turns at 1200 rpm diameter of grinder pulley is 5 inches.

1. Proportion equation
350/1200 = 5/x

2. Cross multiply 
1200*5=250*x
x=(1200*5)/250 = (24*50*5)/(5*50) = 24
The big wheel diameter is 24 inches

For all real numbers, except zero, a x 1/a = 1

Multiplying any real number by it’s reciprocal will result in 1.
This is why a reciprocal of a number is called it’s multiplicative inverse.

The reciprocal of zero is 1/0 and is undefined because dividing by zero is not valid.