Express 16.54 x 10⁻⁵ – 6.76 x 10⁻⁸ + 0.23 x 10⁻⁶ in standard form

Before adding or subtracting numbers in index form, change them all to the same power of 10. The biggest term is 16.54 × 10⁻⁵, which is 1.654 × 10⁻⁴, so use 10⁻⁴ for every term.

6.76 × 10⁻⁸ = 0.000676 × 10⁻⁴ and 0.23 × 10⁻⁶ = 0.0023 × 10⁻⁴.

Now work with the numbers in front: 1.654 − 0.000676 + 0.0023 = 1.655624. So the answer is 1.655624 × 10⁻⁴.

Standard form here is given to three significant figures. Since the fourth figure is 5 (1.655…), we round 1.655624 up to 1.66. The answer is 1.66 × 10⁻⁴.