Question

While Michelle sat observing birds at a bird feeder, one fourth of the birds flew away when they were startled by a noise. Two birds left the bird feeder to go to another stationed a few feet away. Three more birds flew into the branches of a nearby tree. Four birds remained at the feeder. How many birds were at the feeder initially?

Answer 1

12 Birds



To solve this problem, work it from the end towards the beginning.



Number of birds left = 4

Three more birds flew into the branches of a nearby tree. So you lost 3 birds. Add them to the total giving you 7.

Two birds left the bird feeder to go to another stationed a few feet away. So you had a loss of 2 birds. Add them to the total giving you 9.

On fourth of the birds flew away when they were startled by a noise. Now we have something. We know that after one fourth flew away, 9 were left.

X - (1/4)X = 9



Merge the X terms.

(3/4)X = 9



Divide both sides by 3/4

X = 9/(3/4)

X = 9/1 * 4/3

X = 36/3

X = 12



So the number of birds at the feeder initially was 12.

To prove it.

Start with 12. One fourth flew away, leaving 9.

Two more leave, leaving 7.

Three more leave, leaving 4.