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Aptitude Day 43


Problems on Numbers

 1. Three times a positive number is less than its square by 54. Find the number.

Solution:
                Let the number be x.
                x2-3x=54
                x2-9x+6x-54=0
                (x-9)(x+6)=0
                x=9, -6.
 The number is 9.

2. Twice the square of a natural number is equal to the 30 more than the four times of that number. Find the number.

Solution:
                Let the number be x.
                2x2  = 4x+30
                2x2-4x-30=0
                x2-2x-15=0
                x2-5x+3x-15=0
                (x-5)(x-5)=0
                 x=5.
The number is 5.


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