In a two-digit number, if it is known that its unit's digit exceeds its ten's digit by 4 and that the product of the given number and the sum of its digits is equal to 90, then the number is: Pick one:  A) 15  B) 27  C) 38  D) 46  E) 48
Let the ten's digit be x. Then, unit's digit = x + 4. Number = 10x + (x + 4) = 11x + 4   Sum of digits = x + (x + 4) = 2x + 4   (11x + 4)(2x + 4) = 90   22(x)(x) +52x - 74 = 0   (x - 1)(22x + 74) = 0   x = 1   Hence, required number = 11x + 4 = 15.   15NSWER:1511  + 4= 
<gadget id="calculator">11  + 4</gadget>
<output>15</output>
15.   15NSWER:15
<result>A</result>
In a two-digit number, if it is known that its unit's digit exceeds its ten's digit by 4 and that the product of the given number and the sum of its digits is equal to 90, then the number is: