00:03
So here we have the cpi formula or the consumer price index formula, where the new cpi equals the old cpi times 1 plus r over 100 to the nth power, where r is the inflation rate and n is the amount of years later.
00:20
So we are told that the inflation rate is 3 .1%.
00:24
And we are asked how long it will take before the cpi will double.
00:28
So let's go over our variables.
00:30
If we want the new cpi to be twice as much as the old cpi, we can simply write cpi equals 2 cpio, or the old cpi.
00:47
And r is 3 .1, because that is the inflation rate.
00:52
And we are solving for n.
00:53
So now let's plug this information that we have into our formula.
00:57
So we have 2 cpio or the old cpi equals cpio.
01:07
Times 1 plus 3 .1 over 100.
01:13
Remember in this formula, we plug in r as percentage form, not as decimal form, to the nth power...