# IMO Level 1- Mathematics Olympiad (SOF) Class 10: Questions 517 - 520 of 968

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## Question number: 517

### Question

P is twice good a workman as Q and therefore is able to finish a job in 30 days less than Q. Working together they can do it in ________ days.

### Choices

Choice (4) | Response | |
---|---|---|

a. | 50 | |

b. | 30 | |

c. | 20 | |

d. | 40 |

## Question number: 518

### Question

28 integers are chosen from the interval [104,208]. Show that there exit two of them having a common prime divisor.

### Choices

Choice (4) | Response | |
---|---|---|

a. | 1 | |

b. | 0 | |

c. | 3 | |

d. | 2 |

## Question number: 519

### Question

One year ago the ratio between Laxman’s and Gopal’s salary was . The ratios of their individual salaries between last year’s and this year’s salaries are and respectively. At present, the total of their salary is Rs. 4160. The salary of Laxman now, is ________

### Choices

Choice (4) | Response | |
---|---|---|

a. | Rs. 1600 | |

b. | Rs. 2560 | |

c. | Rs. 1040 | |

d. | Rs. 3120 |

## Question number: 520

### Question

P, Q and R start at the same time in the same direction to run around a circular stadium. P completes a round in 280 seconds, Q in 310 seconds and R in 200 seconds, all starting at the same point. After what time will they meet again at the starting point?

### Choices

Choice (4) | Response | |
---|---|---|

a. | 445 minutes 55 seconds | |

b. | 126 minutes 18 seconds | |

c. | 723 minutes 20 seconds | |

d. | 846 minutes 15 seconds |