[ Homework Help ] Open Question : pls help me with these math questions!! answer all those you can answer pls!?

1. how many different numbers can be formed by multiplying some or all of the digits 2, 3, 4, 4, 5, 5,5,5? List all the possible product of such numbers. 2. A year is a leap year if it is divisible by four but not by 100, of it it divisible by 400 (for example, 1900 was not a leap year but 2000 will be). Find the number or leap years from 1884 to 4004 inclusive. 3. Solve for n: P(n,4) = 20C(n - 1, 2) 4. Find the number of nonnegative integer solutions ot the equation x1 + x2 +.. + xr = n, where r and n are positive number. Use the result to find the number of nonnegative integer solutions to the equation x1 + x2 + x3 = 7 List all the possible solutions (x1, x2, x3). 5. A crew of eight men is to be chosen to row an eight-oared boat. If there are eleven men, five of whom can row on the stroke side only, four on the bow side only, and the remaining two on either side, in how many ways may the boat be manned? 6. A music club has sixty member; twenty are sopranos, sixteen are altos, fourteen are tenors, ten are bases. a. How many quartets can be formed in the club? b. How many double quartets can be formed in the club? 7. A class has 2 rows of 8 seats each. there are 14 students 4 of whom always sit in the front row and 5 of whom sit in the back row. How many ways can the students be arranged? 8.Find the sum of all 4 digit numbers which can be formed from the digits 1,2,3 and 4 assuming that a digit cannot be repeated in any one number.

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