If a fly has starts with having 20 babies a day and the babies have 20 every day how many baby flies will there be after one month.?

Answer 1

You give no indication of the life span of the flies - do they die after producing 20 offspring in 1 day, or do they keep on producing flies until the end of the month.

Nor do you specify how many days are in the month.

Assuming an average month of 30 days (since the year has an average of approx 30.44 days per month), then:

Assuming no fly dies and keeps on producing 20 every day, then:

After day 1: 1 adult + 20 babies

After day 2: 21 adult + 420 babies

After day 3: 441 adult + 8820 babies

And so on

After 30 days there are approx 4.1967×10³⁹ babies

Assuming the flies die after producing the babies, then:

After day 1: 20 babies

After day 2: 400 babies

After day 3: 8000 babies

and so on

After 30 days there are approx 1.0737 × 10³⁹ babies

Answer 2

The question is not well defined. Does the first fly keep having 20 babies each day for the rest of the month? How many days in the month - 28, 29, 30 or 31?

If the original fly and its babies keep on having babies until the end of the 31-day month there will be approx 9.7454*10^40 flies.