A rectangular plate has a length of (21.3 0.2) cm and a width of (9.8 0.1) cm. Calculate the area of the plate, including its uncertainty. 36. How many significant figures are in the following num- W bers? (a) 78.9 0.2 (b) 3.788 x 109 (c) 2.46 x 10-6 (d) 0.005 3 37. The tropical year, the time interval from one vernal equinox to the next vernal equinox, is the basis for our calendar. It contains 365.242 199 days. Find the num- ber of seconds in a tropical year.