Question

Which shows the expression below in simplified form? (7 × 10-3) - (2.3 × 10-6) A. 6.9977 × 10-3 B. 6.99977 × 10-3 C. 6.9977 × 10-4 D. 6.977 × 10-3

Answer 1

Option A

`(7 * 10^(-3)) - (2.3 * 10^(-6)) = 6.9977 * 10^(-3)`

Solution:

Given expression is:

`(7 * 10^(-3)) - (2.3 * 10^(-6))`

To evaluate the expression, let us make the exponent of 10 same

`2.3 * 10^(-6) = 0.0023 * 10^(-6+3) = 0.0023 * 10^(-3)`

[ Here, decimal point is moved three times left, so add 3 ]

Therefore,

`(7 * 10^(-3)) - (2.3 * 10^(-6)) = (7 * 10^(-3)) - (0.0023 * 10^(-3))`

`\text{Take the } 10^(-3) \text{ as common }`

`(7 * 10^(-3)) - (0.0023 * 10^(-3)) = 10^(-3)(7-0.0023)\\\\\text{ Solve for terms inside the bracket }\\\\(7 * 10^(-3)) - (0.0023 * 10^(-3)) = 10^(-3) * 6.9977\\\\\text{Therefore, the simplified expression is: }\\\\(7 * 10^(-3)) - (0.0023 * 10^(-3)) = 6.9977 * 10^(-3)`

Thus Option A is correct