In a shop, 40% socks are white and rest are black. 60% socks are made of cotton and rest are made of wool. 25% white socks are made of cotton and 20 of the black socks are made of wool. How many black socks are made of cotton?	Options.
A) 100	B) 80	C) 60	D) 50	E) 25
40% is white -&gt; wht = 0.4x   Blk = 0.6 x   also 60% socks are made of cotton - &gt; ct = 0.6x   wl = 0.4x   we know 25% of the white socks is cotton --&gt; 1/4 (0.4x) = 0.1x = wh-ct   =&gt; 0.3x = wh-wl   total wool is 0.4x =&gt; black wool socks = 0.4 x (total) - 0.3 x (wh-wl) = 0.1x given as 20   =&gt; total number of socks = 200   = &gt; total black socks = .6x = 120   total cotton black socks = 120 - 20 (bl-wl) = 100 hence 100
<result>A</result>
In a shop, 40% socks are white and rest are black. 60% socks are made of cotton and rest are made of wool. 25% white socks are made of cotton and 20 of the black socks are made of wool. How many black socks are made of cotton?