Lead-202 has a half-life of 53,000 years. How long will it take for 15/16 of a sample of lead-202 to decay? 106,000 years
159,000 years
212,000 years
265,000 years
(Thank you very much :L)

1) what is the power in horsepower of a 100 watt light bulb? what is the power in kilowatts of a 200 horsepower engine? 2) if a cars engine is providing 3000 n of force to keep the car moving at 5 m/s, what is the engine’s effective power? 3) how many gallons of water will be pumped from a well 30 feet deep by a 1/2 hp engine in 1 minute? (1 gallon weighs 8.34 pounds)