Question

Cassie added two numbers together on her calculator for her biology homework. The calculator showed the sum as 9.62E-6. She knows she used 0.000009535 as one of the numbers. What number did she add to 0.000009535 to get 9.62E-6?
A.
1.8 × 10^-6
B.
8.5 × 10^-6
C.
1.8 × 10^-8
D.
8.5 × 10^-8

Answer 1

To find the number that Cassie added to \(0.000009535\) (which is equivalent to \(9.535 \times 10^{-6}\)) to get \(9.62E-6\) (which is equivalent to \(9.62 \times 10^{-6}\)), we set up the equation:

\[
x + 9.535 \times 10^{-6} = 9.62 \times 10^{-6}
\]

Next, we can solve for \(x\) by isolating it:

\[
x = 9.62 \times 10^{-6} - 9.535 \times 10^{-6}
\]

Now, carrying out the subtraction:

\[
x = (9.62 - 9.535) \times 10^{-6}
\]
\[
x = 0.085 \times 10^{-6}
\]

To express \(0.085 \times 10^{-6}\) in scientific notation, we write:

\[
0.085 = 8.5 \times 10^{-2}
\]

So:

\[
x = 8.5 \times 10^{-2} \times 10^{-6} = 8.5 \times 10^{-8}
\]

Thus, the number that Cassie added is:

**D. \(8.5 \times 10^{-8}\)**.