  We show that the neglect of the $(V-A)\times (V+A)$ pieces of the electroweak
penguin (EWP) amplitudes in the effective hamiltonian (the Wilson coefficients
are very small) allows one to calculate the relative size of some tree and EWP
diagrams in $B \to \pi \pi$ and $B\to \pi K$ decays. For both decay classes,
tree and EWP amplitudes are related using only isospin. In $B\to \pi \pi$, the
ratio $C/T$ is calculated using isospin alone; in $B\to \pi K$ it is found
using flavor SU(3) symmetry. These results are obtained by computing explicitly
all Wick contractions of all effective operators. Relations among these
contractions are found using Fierz identities and final-state symmetry
arguments.
