Question

World population increased from 2.3 billion in 1900 to 6.1 billion in 2000. What was the percent of increase?

Answer 1

165.2173913043% increase

Explanation:

To work out the percentage increase, we first need to find out the increase between 2.3 billion and 6.1 billion, which is 3.8 billion.

Then we can work out the percentage difference by (percentage change)/(original amount) x 100. Then substitute the numbers in to get to an answer of 165.2173913043% increase. If your number is negative then there is a percentage decrease

Answer 2

`165.21%` to 2 decimal places

Explanation:

As we are only interested in percentages the degree of the count is of no consequence ( as long as they are of the same units). Thus we can write the relationship as:

`("change")/("original value") -> (6.1-2.3)/2.3 = 3.8/2.3`

Short cut method with a slight variant to demonstrate why we have %

`color(green)(3.8/2.3color(red)(xx1)" "=" "3.8/2.3color(red)(xx100/100)" "=" "3.8/2.3color(red)(xx100xx1/100))`

But another way of writing `1/100` is % giving

`color(green)(=3.8/2.3color(red)(xx100%))`

`color(green)(=165.21%)` to 2 decimal places
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If you have to divide manually and you do not like dividing decimals you could write `3.8/2.3" as "38/23`. You get the same answer.