Explanation:
"increase" means to take the original 100% and put an additional 3.5% of these 100% on top of it.
so, we have to calculate
100% + 3.5% of £16470.45
100% of £16470.45 = £16470.45 × 100/100
3.5% of £16470.45 = £16470.45 × 3.5/100
the sum is therefore
£16470.45 × (100/100 + 3.5/100) =
= £16470.45 × (1 + 0.035) = £16470.45 × 1.035 =
= £17,046.91575 ≈ £17,046.92