self Maths Puzzle

there is a 100 mtr race between a hare and a tortoise. speed of hare=10m/s and dat of tortoise is 1m/s. tortoise starts 10 m ahead of hare in the begining. that is hare starts from 0m and hare from 10m. evidently the hare takes 10s to complete race and tortoise 90 secs, which means hare wins. but now if we try applying calculus. when hare covers 10m tortoise covers 1 m(from start). every time the hare reaches previous position of tortoise, the tortoise advances by some distance(however small it may be). thus if we take limit->0 we shall see dat the hare will never cross the tortoise. Is this contradiction possible??

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self Other Question

It is a 6 digit number.
Sum of 3rd and 4th digits is equal to Sum of 2nd and last digit.
5th digit is double of 2nd digit.
1st digit is equal to sum of 2nd and 4th digits.
3rd digit is double of 4th digit.
Final Clue: 5th digit is three greater than 2nd digit.

Find that number
If a person have coins of only two denominations (among 5,20,25,50 paisa),in such a way that if quantity of one denomination is multiplied by its value and again multiplied by 4, it's equal to the amount obtained when other denomination coin is multiplied by its value. Find these two types of coins.