The pondage of a certain dam this year decreased by 17.5% compared with last year and decreased by 34% compared with the year before last.
What% did the pondage last year decrease compared with the year before last?
What% did the pondage last year decrease compared with the year before last?
Answer
Therefore, the ratio that decreased is ( 5 - 4) / 5 = 0.2 = 20%.
20%
Solution
Assuming pondage of this year to be 100.
Pondage of the last year is 100/ (1-0.175) = 1000/825 = 40/33.
Pondage of the year before last is 100/ (1 - 0.34) = 100/66 = 50/33.
40/33 : 50/33 = 4 : 5.
Pondage of the last year is 100/ (1-0.175) = 1000/825 = 40/33.
Pondage of the year before last is 100/ (1 - 0.34) = 100/66 = 50/33.
40/33 : 50/33 = 4 : 5.
Therefore, the ratio that decreased is ( 5 - 4) / 5 = 0.2 = 20%.
