You pay $2.40 for 3/4 pound of grapes. Your friend buys a pound of grapes at the same time and estimates that he will pay $1.80. What can you say about your friend's estimate?
Your friend's estimate is wrong because you pay $2.40 for 3/4 pound of grapes, which means 1/4 pound of grapes equals $0.80, you friend wants to any for one pound, so your friend must use 1/4 times 4 equals $0.80 times 4=$3.20 for a pound of grapes
