Source: 300 Moscow Puzzles
Problem: Mother asked Vera to type a manuscript for her. Vera said she will type
20 pages a day. Vera was lazy during the first half of the manuscript and
typed at speed of 10 pages per day and the latter half of the script at 30
pages per day.
Vera said, see I made it on time half of 30 + 10 is 20 which is my average.
Mother said ‘No, You didn’t’.
Who was right and why?
Problem: Mother asked Vera to type a manuscript for her. Vera said she will type
20 pages a day. Vera was lazy during the first half of the manuscript and
typed at speed of 10 pages per day and the latter half of the script at 30
pages per day.
Vera said, see I made it on time half of 30 + 10 is 20 which is my average.
Mother said ‘No, You didn’t’.
Who was right and why?
Here the variable change is not number of pages its no. of days
ReplyDeleteX days of work will yield 20x pages acc. To her promise…
But Ist half of her manuscript i.e. 20x/2 are completed in y days which gives x = y,
While x should have been equal to y + y’, where y’ is for second half.
So here y’ = 0.
Vera will need to complete it in no time.
So ”Mother is always right” !!