Calculating Cumulative Time Changes over 20 Centuries

[Fletcher]

The exercise:

Assuming the length of the day uniformly increases by 0.0010s per century, calculate the cumulative effect on the measure of time over 20 centuries.

The answer given in the book:

2.1 hours

My initial thought was 0.001 x 20, but that's apparently wrong. I think I'm missing something basic.

 

[ovoleg]

Everyday it increases uniformly by .001s per century so in one century each day will be .0001s longer. How much total time does this add on in 20 centuries?

 

[Doc Al]

My initial thought was 0.001 x 20, but that's apparently wrong. I think I'm missing something basic.

What you calculated is the increased length of a single day after 20 centuries. What's the average increase per day? How many days in 20 centuries?