PSR 1937+or-21 rotates once every 1.557 806 448 872 75+or-3ms, Where the tailing +or- indicates the uncertaint

Question

in the last decimal place (it does not mean +or-3 ms.

a) How may rotations does PSR make in 7.00days
b)how much thime does the pulsar talke to rotate exactly one million times and
c)What is the associated uncertainty ?

I really need help in this so pleace show me how to get the right answer not just the answer. I want to understand not just get an answer for it.

Answer 1

There are 24*60*60*1000 ms in one day. Divide this number by 1.557 806 448 872 75 to get the nominal number of rotations in one day. Then repeat the division for the upper and lower limits of uncertainty, 1.557 806 448 872 78 and 1.557 806 448 872 72. The difference between these latter numbers and the nominal number is the uncertainty in the result.

The time it takes the pulsar to rotate 1,000,000 times is 1,000,000 times 1.557 806 448 872 75 (ms); this is the nominal value. Again multiply 1,000,000 by the upper and lower limits of uncertainty, 1.557 806 448 872 78 and 1.557 806 448 872 73, and find the differences from the nominal value to get the uncertainty in the answer.