In the parallel circuit, if the current put out

Question

by the battery is 3 A and the current through
R1 is 1 A, what is the current through R2?

Answer 1

If R2 and R1 are in parallel, the fraction of the 3A that goes through R2 is
(1/R2)/[(1/R1 + 1/R2)]
= 1/[(R2/R1) + 1]