Method of Substitution to Find the Solution of a Pair of Linear Equations
A two digit n...
Question
A two digit number is obtained by multiplying the sum of the digits by 8. Also, it is obtained by multiplying the difference of the digits by 14 and adding 2. Find the number.
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Solution
Call the two-digit number xy, where x is the tens and y is the ones. Its value is 10x + y. Then we can write 8(x + y) = 10x + y and 14(x - y) + 2 = 10x + y Simplifying these we get 8x + 8y = 10x + y
7y = 2x (or 14y = 4x) and 14x - 14y + 2 = 10x + y 4x + 2 = 15y Substitute from above and get 14y + 2 = 15y y = 2 so then x = 7 Your number is 72.