Question

The house sparrows population has decreased by 41% since 1977. The population is now approximately 6.5 million pairs of birds. What was the estimated sparrow population in 1977?

Answer 1

Let x be estimated population in 1977

x - 0.41x  = 6,500,000
 x = (6,500,000 / 0.59

Answer is approximately 11,017,000  

11 million