Assume the world catch of fish in 1950 was 12 million tons and in 1955 it was 96 million tons.

find the average rate of change from 1950 to 1995.

The rate of change is 16.8 million tons per year

Solution:

Given that, the world catch of fish in 1950 was 12 million tons and in 1955 it was 96 million tons

The average rate of change is given by formula:

Value in 1950 = 12 million tons

Value in 1955 = 96 million tons

Change in value = value in 1955 - value in 1950

Change in value = 96 million - 12 million = 84 million tons

Number of years = 1950 to 1955 = 5 years

Substitute the given values in formula,

Thus rate of change is 16.8 million tons per year

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

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note: the best i know.