Question

In a newspaper, it was reported that yearly robberies in Springfield were up 50% to 279 in 2012 from 2011. How many robberies were there in Springfield in 2011? In a newspaper, it was reported that yearly robberies in Springfield were up 50% to 279 in 2012 from 2011. How many robberies were there in Springfield in 2011?

Answer 1

186

Explanation:

In a newspaper, it was reported that yearly robberies in Springfield were up 50% to 279 in 2012 from 2011. How many robberies were there in Springfield in 2011?

Robberies up: percent increase

(# robberies in 2011)(1+r)=# robberies in 2012

x(1+0.5)=279

x(1.5)=279

(x(1.5))/1.5 = 279/15

x=186

There were 186 robberies in 2011

Answer 2

There were 186 Springfield robberies in 2011

Explanation:

Think about what happens when you double a number.

You multiply it by 2. Since it's been doubles, we say is has had a 100% increase.

Likewise a 50% increase correlates to multiply by 1.5

Since we are trying to find the previous amount that experienced the increase, we divide by 1.5 to find the original amount because that amount*1.5 gives us 279.

Calling the original r, it is clear that 1.5r=279.

Solving for r, we find the original # of robberies to be 186.