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    IBHardNumber7–9

    The Price Before the VAT Was Added

    O Preço Antes de o IVA Ser Acrescentado

    A pair of headphones costs 172.20 euros including VAT at 23\%. Find the price before VAT, and explain why subtracting 23\% of 172.20 gives the wrong answer.

    Decide first which amount the 23\% was calculated on — that amount is the unknown, not the price on the label. Once you know what the label represents as a percentage of the unknown, the operation follows.

    Solution

    Step 1 of 5

    1. 1.Let p be the price before VAT. The VAT is 23\% of p, so the label is 123\% of p: