On an article the profit is 210% of the cost price. If the cost price increases by 40% but the selling price remains constant, approximately what per cent of selling price will be the profit?

C.P. of article = Rs. 100 (let)

∴ Its S.P. = Rs. (100 + 210) = Rs. 310

New C.P. of article = Rs. 140

$herefore$ Required profit per cent $=frac{ ext { S.P. }- ext { C.P. }}{ ext { S.P }} imes 100$

$=left(frac{310-140}{310} ight) imes 100=frac{1700}{31}=54.838 approx 55 \%$