The amount of weight that sam loses is directly proportional to the number of hours he spends exercising. if sam loses a pound of weight for each 3 hrs of exercise, how many hours must he spend exercising to lose 25 lbs?

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Cora bought a package of erasers. there are 4 pink erasers and 12 blue erasers. what is the ratio of pink erasers to blue erasers?

Astuntman jumping off a 20-m-high building is modeled by the equation h=20-5t^2, where t is the same in seconds. a high-speed camera is ready to film him between 15m and 10m above the ground. for which interval of time should the camera film him?