I used the slightly longer formula for parallel resistance when R1 and R2 are not the same. The sum of R1xR2 ÷ by the sum of R1 + R2. In my case R1 and R2 are each .9Ω. So .9 x .9 = .81. and .9 + .9 = 1.8. So .91 ÷ 1.8 = .45. Just a longer way a... Login to read more.