Chapter 1 - Sections 1.1-1.8 - Exercises - Cumulative Problems - Page 41: 111b

$1.59 \times 10^{-2}$

1. Rearrange the numbers to have the same exponent part, and then we simply make a common addition and subtraction $1.87 \times 10^{-2} + 2 \times 10^{-4} -3 \times 10^{-3} =1.87 \times 10^{-2} + 0.02 \times 10^{-2} -0.3 \times 10^{-2} = 1.59 \times 10^{-2}$