I have 100 values and I want to find out how many iterations it takes for
each value to get to 0, each value decreases by 20% each month. Thanks.

If a value starts with a non-zero amount, then it can NEVER reach zero if it
decrease by 20% of its residual value.

If you decrease it 20 % of its original value it will take 5 Iterations:

100
80
60
40
20
0

--
Gary''s Student - gsnu200720

Sorry I forgot to write that if you start out at 100 how many iterations does
it take to go below 50...using the residual value

"Gary''s Student" wrote:

If a value starts with a non-zero amount, then it can NEVER reach zero if it
decrease by 20% of its residual value.

If you decrease it 20 % of its original value it will take 5 Iterations:

100
80
60
40
20
0

--
Gary''s Student - gsnu200720

In A1 put 100 and
In A2 thru A10 enter:

=A1*0.8
=A2*0.8
=A3*0.8
=A4*0.8
=A5*0.8
=A6*0.8
=A7*0.8
=A8*0.8
=A9*0.8
to see:

100
80
64
51.2
40.96
32.768
26.2144
20.97152
16.777216
13.4217728

and as you can see 4 iterations got use below 50.
--
Gary''s Student - gsnu200720


"Rick" wrote:

Sorry I forgot to write that if you start out at 100 how many iterations does
it take to go below 50...using the residual value

"Gary''s Student" wrote:

If a value starts with a non-zero amount, then it can NEVER reach zero if it
decrease by 20% of its residual value.

If you decrease it 20 % of its original value it will take 5 Iterations:

100
80
60
40
20
0

--
Gary''s Student - gsnu200720

Or something like this

# iterations =LOG(EndVal/BeginVal)/LOG(0.8)

"Gary''s Student" wrote:

In A1 put 100 and
In A2 thru A10 enter:

=A1*0.8
=A2*0.8
=A3*0.8
=A4*0.8
=A5*0.8
=A6*0.8
=A7*0.8
=A8*0.8
=A9*0.8
to see:

100
80
64
51.2
40.96
32.768
26.2144
20.97152
16.777216
13.4217728

and as you can see 4 iterations got use below 50.
--
Gary''s Student - gsnu200720


"Rick" wrote:

Sorry I forgot to write that if you start out at 100 how many iterations does
it take to go below 50...using the residual value

"Gary''s Student" wrote:

If a value starts with a non-zero amount, then it can NEVER reach zero if it
decrease by 20% of its residual value.

If you decrease it 20 % of its original value it will take 5 Iterations:

100
80
60
40
20
0

--
Gary''s Student - gsnu200720

Very good. Only a single cell and no need to iterate. Looks like thresholds
for exponential decay.
--
Gary''s Student - gsnu200720

I tried the log function below but it did not work...it gave me -12 something.

"Barb Reinhardt" wrote:

Or something like this

# iterations =LOG(EndVal/BeginVal)/LOG(0.8)

"Gary''s Student" wrote:

In A1 put 100 and
In A2 thru A10 enter:

=A1*0.8
=A2*0.8
=A3*0.8
=A4*0.8
=A5*0.8
=A6*0.8
=A7*0.8
=A8*0.8
=A9*0.8
to see:

100
80
64
51.2
40.96
32.768
26.2144
20.97152
16.777216
13.4217728

and as you can see 4 iterations got use below 50.
--
Gary''s Student - gsnu200720


"Rick" wrote:

Sorry I forgot to write that if you start out at 100 how many iterations does
it take to go below 50...using the residual value

"Gary''s Student" wrote:

If a value starts with a non-zero amount, then it can NEVER reach zero if it
decrease by 20% of its residual value.

If you decrease it 20 % of its original value it will take 5 Iterations:

100
80
60
40
20
0

--
Gary''s Student - gsnu200720