significant numbers are numbers that 'have meaning' to it. This is any digit that is not a 0.
inside the decimal 0.003689, the digits 3, 6, 8, & 9 are all significant figures
rounded to only 3 significant figures.
9 is greater than 5, therefore, round upwards
0.003689 rounded becomes 0.00369
0.00369 is your answer
hope this helps
