The 20 ounce bottle because you get more for .90 cents more
Marvin has got to go 20 blocks south because think of it as a drawing. Each line is 10 blocks. He will end up back in line with the bakery and all he has to go is back down 20 blocks
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You should just have to divide the weight lost (4.5 ounces) by the time it took for her cat to lose that weight (4 weeks)!
4.5 / 4 = 1.125, meaning her cat lost about 1.125 ounces per week!