Let the price of a pen be 'x' and that of pencil be 'y' Then 87x + 29y = 783Multiplying eqn (i) by 30/29 we get (87x) x 30/29 + (29y) 30/29 = 783 x 30/29∴ 90x + 30y = 810
S.P. per metre = 8200/40 = Rs. 205∴ C.P. per metre = Rs. (205 - 25) = Rs. 180∴ C.P. of 40 metre cloth= Rs. (40 x 180) = Rs. 7200∴ Gain = Rs. (8200 - 7200) = Rs. 1000