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.
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.