Question

What is the sum of (1.3 × 10-7) and (-3.8 × 10-3)?
A. 2.5 × 10-10
B. -2.5 × 10-4
C. 3.8 × 10-3
D. -3.8 × 10-3

Answer 1

1.3 x 10⁻⁷ + -3.9 x 10⁻³

1.3 x 10⁻⁷ = 0.00000013
-3.9 x 10⁻³ = -0.0039

-  0.00390000
+ 0.00000013   
 - 0.00389987 ⇒ -3.8 x 10⁻³  CHOICE D.