# Aptitude - Problems on Numbers

- Problems on Numbers - Formulas
- Problems on Numbers - General Questions
- Problems on Numbers - Data Sufficiency 1
- Problems on Numbers - Data Sufficiency 2

*Directions to Solve*

Each of the questions given below consists of a question followed by three statements. You have to study the question and the statements and decide which of the statement(s) is/are necessary to answer the question.

What is the two-digit number? | |

I. | The difference between the two-digit number and the number formed by interchanging the digits is 27. |

II. | The difference between the two digits is 3. |

III. | The digit at unit's place is less than that at ten's place by 3. |

Let the tens and units digit be *x* and *y* respectively.

I. (10*x* + *y*) - (10*y* + *x*) *x* - *y* = 3.

II. *x* - *y* = 3.

III. *x* - *y* = 3.

Thus, even all the given three statements together do not give the answer.

Correct answer is (E).

What is the two-digit number? | |

I. | Sum of the digits is 7. |

II. | Difference between the number and the number obtained by interchanging the digits is 9. |

III. | Digit in the ten's place is bigger than the digit in the unit's place by 1. |

Let the tens and units digit be *x* and *y* respectively.

I. *x* + *y* = 7.

II. (10*x* + *y*) - (10*y* + *x*) = 9 *x* - *y* = 1.

III. *x* - *y* = 1.

Thus, I and II as well as I and III give the answer.

Correct answer is (E).