Snow is approximately 1/8 as heavy as water how many inches of snow would it take to weigh as much as 3 1/2inches of rain fall

Snow is 1/8 as heavy as water.

That means 1 cu. Inch of rainfall results in 1/8 cu. Inch of snow

So, 3.5 cu. Inch of rainfall results in [ 1/8 * 3.5] cu. Inch of snow

0.4375 cu. Inch of snow

Therefore 0.4375 cu. Inches of snow would weigh as much as 3.5 cu. inches of rainfall.