Unless you're using a calculator, you have to have both in the same form before they can be added. 2.3 x 10-1 = 0.23 145.75 + 0.23 = 145.98 And if you like, = 1.4598 x 102 . Here's the other...
25600 = 2.56*103. The number has 3 sig figs.
8.62 x 103
take the negative logarithm ex. 10^-4 has a pH of 4
20,000 + 3,400,000