The price of an article is reduced by 30% but the daily sale of the article increased by 35%. The net percentage effect on the daily sale receipts is:

$6\frac{1}{2}$ % decrease

30% = \(\frac{3}{10}\)

35% = \(\frac{27}{20}\)

Price =   10               7

Sale =   20               27

    ———————————————

          200              187

Daily receipt educed by 13 = \(\frac{13 × 100}{200}\) = 6\(\frac{1}{2}\)%