Method of Substitution to Find the Solution of a Pair of Linear Equations
One says," gi...
Question
One says," give me a 100, friend! I shall then become twice as rich as you". The other replies, "If you give me 10, I shall be six times as rich as you." Tell me what is the amount of their capital?
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Solution
Let first person be A and second person be B Let A have x and B have y initially, If B gives A 100, then A becomes twice as rich as B So x+100 = 2(y-100) (1) If A gives B 10 then B becomes 6 times as rich as A So y+10 = 6(x-10) (2)
From (1) x+100 = 2y-200 => x-2y= -300 (3) From (2) y+10=6x-60 => 6x-y = 70 (4) Multiply (3) by -6 and add to (4) -6x+12y=1800 6x-y = 70 ------------------- 11y =1870 y = 170 substitute in (3) x-2(170) = -300 x-340= -300 x= 40 Answer" 40 and 170