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7.5Solve following questions.In a two digit number, the digit at unit's place isequal to the square of the digit at ten’s place. If54 is added to the number, the digits get inter-changed. Find the number.

Answer»

your answer would be 39

let numbers at one place =2x; ten's place be = x; 10(x) + 1(2x)=10x+2x; 10x + 2x = 3x + 18; 12x-3x=18; 9x=18; x=18/9=2; the digit at one's place = 2x X = 2x2=4; digit in ten's place = x =2; the numbers is 10( x)+12(×) = 10(2)+1(2x)=20+(4)=24

let tenth place digit = xunit digit = x^2no = 10x+x^254 added digit reversenew no 10x^2+x10x^2+x= 10x+x^2+549x^2-9x=549(x^2-x)= 54x^2-x-6=0.x^2-3x+2x-6=0x(x-3)+2(x-3)=0(x-3)(x+2)=0x= -2(impossible)x= 3so nos= 10x+x^2 = 10×3+9 = 39


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