Question: Which deal costs less per gram?
A) $5 for 500g
B) $3 for 250g
Predict: I thought this question would be about addition.
Clarify: I had nothing to clarify.
Find the big picture: What deal is better?
First I worked out that $5 for 500g was $1 per gram.
Then I worked out that 250g+250g was 500g, but 3+3 is 6, so B would be $6 for 500g, while A is $5 for 500g.
So A is the answer because it cost less than B.
Summary: I used my prior knowledge.