# The estimated population of the world was 1.6 billion in 190 and 4.0 billion in 1975. What was the percent increase?

Nov 4, 2017

In 1900, there were 1.6bn people,
That means that in 1900 1.6bn was 100%
So,
percent increase is,
$\frac{16}{10} \times \frac{100 + x}{100} = 4$
$\frac{1600 + 16 x}{1000} = 4$
$1600 + 16 x = 4000$
$16 x = 2400$
$x = \frac{2400}{16}$
$x = 150$
There was a 250% increase.
There was a 250% increase because it is $100 + x$

Nov 4, 2017

150%

#### Explanation:

In $1990$ the population was $1.6$ billion (16/10) people. In $1975$ it was $4$ billion. We need to find the percent increased.

Let it be $x$

We need to build an equation. We know that when we add $x$ percent of $1.6$ to $1.6$, it gives us $4$

So,

$\rightarrow 1.6 + 1.6 \times \frac{x}{100} = 4$

$\rightarrow \frac{16}{10} + \frac{\frac{16}{10} x}{100} = 4$

$\rightarrow \frac{160 + \frac{16}{10} x}{100} = 4$

$\rightarrow 160 + \frac{16}{10} x = 4 \times 100$

$\rightarrow 160 + \frac{16}{10} x = 400$

$\rightarrow \frac{16}{10} x = 240$

$\rightarrow x = {\cancel{240}}^{15} \times \frac{10}{\cancel{16}} ^ 1$

color(green)(rArrx=150%

Hope this helps!!! ☺•☻