Question

Cost of B is 200 more than cost of A ,Asold at profit of 20%and B sold at loss of 30% ,the selling price ofA:B is 6:7 then cost price of B is?

Answer 1

let the c.p. of A = rs 100a
so the c.p. of B = rs (100a+200)

s.p. of A = c.p.of A + profit on A = 100a + 20% of 100a = 100a + 20a = rs (120a)

similarly, s.p. of B = c.p. of B - loss on B = (100a + 200) - 30% of (100a + 200) = (100a + 200 )-30% * 100(a+2) = (100a + 200) - 30(a +2) = 100a +200 -30a -60 = rs (70a + 140)

but s.p. of A/s.p. of B = 6/7

so, (120a)/(70a +140) = 6/7
cross multipying

7*(120a) = 6*(70a +140)
840a = 420a + 840
420a = 840
a = 2

so the cost price of B= 100a + 200 = 100*2 +200 = 200 + 200 = rs 400

hope this might help