Quick Answer: Since Helix was exposed to the sun for 5 minutes without protection, he had only 3 minutes left before he would burn. A sunscreen with an SPF of 10 would extend the time left to 30 minutes. Complete Solution: An SPF 10 product used before going in the sun, and when the user normally burns in 8 minutes, provides about 8x10, or 80 minutes of protection. Putting the lotion on 5 minutes after being in the sun uses 5/8 of the time before being burned. Thus, 3/8 of the normal protection time before burning is left. Because (3/8)(80) is 30, a person has 30 minutes before burning. Note: The limits of safe exposure to sunlight vary by individual, season, and geographic location.
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