40% or 40/100 which is in decimal format 0.4.
50% or 50/100 which is in decimal format 0.5.
P( tueday AND friday) <----- AND is a keyword, means product
P(tuesday) AND P(friday)
0.4 * 0.5
0.2 or 0.2 * 100 or 20% chance that it will rain on both days.