What is the approximate percent decrease when a fish count goes down from 850 to 500? The percent decrease is approximately 40%.
The percent decrease is approximately 70%.
The percent decrease is approximately 140%.
The percent decrease is approximately 240%..

Approximate decrease is 70%

Step-by-step explanation:

The percent decrease is the change over the new original / final value.  The change between the old and the new is 850 - 500, which is 350.  Thus the approximate percentage difference is

350

500

A quick way to turn anything with a denominator that starts with 5 and any number of zeros after it ... is to multiply both the top and bottom by 2.  That is, that turns the ratio above to:

700

1000

Since a percentage is a number of 100, not 1000, just divide everything by 10.  That means take away a zero from each number, which gives you a fraction of:

70

100

Thus, the result is 70/100, or 70%.

b

Step-by-step explanation:

10% of increase is the final answer! : )