Your car insurance premium was $400 before the increase. This is the starting value. After the increase, it costs $450. This is the end value.
In our example, $450 - $400 = a $50 increase.
In our example, $50 / $400 = 0. 125.
The final answer to our example is 0. 125 x 100 = 12. 5% increase in auto insurance premiums.
There’s a trick to these problems with many zeroes. Instead of counting the zeroes each step of the way, we can rewrite these as 5. 3 billion and 7. 4 billion.
7. 4 billion ÷ 5. 3 billion = about 1. 4. We’ve rounded to two significant digits because that’s how many there were in the original problem.
1. 4 x 100 = 140%. This means the world population in 2015 is 140% the size of the population in 1990.
140% - 100% = a 40% increase in population. This works because starting value + increase = end value. Rearrange the equation and we get increase = end value - starting value.
