30. A certain two-digit number has avalue that is three times the sum of itsdigits. Also, the units digit is one morethan tree times the tens digit. Find the number Ans.: 27
31. A two-digit number is such that the product of its digits is 18. When 63 is subtracted from the number, thedigits interchange their positions. Find the numbers. Ans.: 92
32. The sum of the digits of a three-place number is 19. If the tens and unitsdigits are interchanged the number isdiminished by 27, and if the hundreds and tens digits are interchanged the number is increased by 180. What is the number? Ans.: 685
33. It takes 15 minutes to boil an egg.How could you boil the egg having two hourglasses that measure 7 and 11 minutes?