We just studied if A, then B. The contrapositive is if you reverse and negate that.
If momma bear crosses the river, so does baby bear. Contrapositive: If the baby didn’t cross, then momma didn’t, either.
Those who contrapose will do well on the LSAT (contrapose: the act of making a contrapositive). Why? You can take conditional rules and double them by contraposing the original conditional.
Negate Values to make Contrapositive
Two Valid Conditionals
And, poof!, it becomes two valid conditionals after you contrapose the original (reverse the statements and negate them).
Here’s a minor diversion into pop culture and formal logic.
1) It don’t mean a thing if it ain’t got that swing.
~has swing → ~mean anything
Contrapositive: means anything → has swing
2) You must take the A Train,
If you want to go to Harlem.
go to Harlem → take the A train
Contrapositive: ~take the A train → ~go to Harlem