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- IN THE LAST SEVERAL WEEKS,
17 DAYS SAW RAIN AND 11 DAYS SAW HIGH WINDS.
IN THAT SAME TIME PERIOD,
FOUR DAYS SAW BOTH RAIN AND HIGH WINDS.
HOW MANY DAYS SAW EITHER RAIN OR HIGH WINDS?
LET'S SOLVE THIS USING A VENN DIAGRAM
WHERE SET R REPRESENTS THE DAYS THAT SAW RAIN
AND SET W REPRESENTS THE DAYS THAT SAW HIGH WINDS.
NOTICE HOW WE'RE TOLD FOUR DAYS SAW BOTH RAIN AND HIGH WINDS,
AND THAT MEANS THERE WILL BE FOUR DAYS IN THE INTERSECTION
OF SET R AND SET W FOR THIS REGION HERE.
AGAIN, THERE ARE FOUR DAYS IN THIS REGION HERE
BECAUSE FOUR DAYS SAW BOTH RAIN AND HIGH WINDS.
YOU'LL NOTICE HOW WE'RE ALSO TOLD THAT 17 DAYS SAW RAIN,
WHICH MEANS THERE WOULD BE 17 DAYS IN SET R
BUT NOTICE HOW FOUR OF THOSE DAYS
HAVE ALREADY BEEN ACCOUNTED FOR BECAUSE THOSE DAYS
SAW RAIN AND HIGH WIND.
NOTICE HOW THAT WOULD LEAVE 17 - 4 OR 13 DAYS
THAT ONLY SAW RAIN, WHICH WOULD BE 13 DAYS
IN THIS REGION HERE.
THESE 13 DAYS ONLY SAW RAIN BUT NOT HIGH WINDS.
AND THEN WE'RE ALSO TOLD THAT 11 DAYS SAW HIGH WINDS.
SO THERE ARE 11 DAYS IN SET W BUT AGAIN,
FOUR OF THEM ARE ALREADY ACCOUNTED FOR.
SINCE 11 - 4 = 7,
THERE WOULD BE SEVEN DAYS IN THIS REGION HERE
TO REPRESENT THE NUMBER OF DAYS THAT ONLY SAW HIGH WINDS,
WHICH WOULD BE IN THIS REGION HERE.
OUR GOAL HERE IS TO FIND THE NUMBER OF DAYS
THAT SAW EITHER RAIN OR HIGH WINDS, WHICH MEANS THE DAYS
THAT SAW ONLY RAIN OR RAIN AND WIND OR JUST WIND.
USING SET NOTATION, THIS WOULD BE THE NUMBER OF ELEMENTS
OR THE NUMBER OF DAYS IN THIS CASE OF R UNION W,
MEANING THE NUMBER OF ELEMENTS OR DAYS IN SET R OR SET W,
WHICH IS EQUAL TO 13 + 4 + 7, WHICH IS 24.
SO WE CAN SAY 24 DAYS SAW EITHER RAIN OR HIGH WINDS.
I HOPE YOU FOUND THIS HELPFUL.