A mother asked her daughter to type a manuscript. The daughter claimed: " I will type an average of 20 pages a day."
She typed the first half of the manuscript rather lazily, at 10 pages a day. To make up for it, she typed the second half at 30 pages a day. "See, I did average 20 pages a day", the daughter concluded.
"No, you didn't," her mother said.
Who was right?
Mom is correct.... pick an example say manuscript is 120 pages
60 pages at 10/day = 6 days
60 pages at 30/day = 2 days
8 days total 120 pages/8days = 15 pages per day average
You can try it with other manuscript #'s too....results are the same.....
let 2x be the number of pages then x = 1/2 of the pages
x pages / ( x pages /10 pages/day + x pages / 30 pages/day) = average
2/(1/10 + 1/30) = 15 pages/day